How to reproduce: 

public partial class RadForm1 : Telerik.WinControls.UI.RadForm
{
    public RadForm1()
    {
        InitializeComponent();

        this.radGridView1.DataSource = this.GetData();
        this.radGridView1.AutoSizeColumnsMode = Telerik.WinControls.UI.GridViewAutoSizeColumnsMode.Fill;

        GridViewDecimalColumn decimalColumn  = this.radGridView1.Columns[0] as GridViewDecimalColumn;
        decimalColumn.DecimalPlaces = 2;
        decimalColumn.FormatString = "{0:N2}";
        decimalColumn.ExcelExportType = DisplayFormatType.Custom;
        decimalColumn.ExcelExportFormatString = "0.000";
    }

    public object GridViewSpreaExport { get; private set; }

    private object GetData()
    {
        DataTable dt = new DataTable();
        dt.Columns.Add("Id", typeof(double));
        dt.Columns.Add("Name", typeof(string));
        dt.Columns.Add("Bool", typeof(bool));
        dt.Columns.Add("Date", typeof(DateTime));

        for (int i = 0; i < 100; i++)
        {
            dt.Rows.Add(1.10 + i, "Name " + i, i % 2 == 0, DateTime.Now.AddDays(i));
        }

        return dt;
    }

    private void radButton1_Click(object sender, EventArgs e)
    {
        GridViewSpreadStreamExport spreadExporter = new GridViewSpreadStreamExport(this.radGridView1);
        spreadExporter.FileExportMode = FileExportMode.CreateOrOverrideFile;
        SpreadStreamExportRenderer renderer1 = new SpreadStreamExportRenderer();
        spreadExporter.RunExportAsync(@"..\..\exported-stream.xlsx", renderer1);

    }
}

Workaround: Create a custom SpreadStreamExportRenderer

public class CustomSpreadStreamExportRenderer : SpreadStreamExportRenderer
{
    public override void SetCellValue(DataType dataType, object value)
    {
        switch (dataType)
        {
            case DataType.Number:
                this.SetNumberValue(value);
                break;
            case DataType.DateTime:
                this.SetDateTimeValue(value);
                break;
            case DataType.Boolean:
                this.SetBooleanValue(value);
                break;
            case DataType.Other:
                if (this.SetNumberValue(value))
                {
                    break;
                }
                if (this.SetDateTimeValue(value))
                {
                    break;
                }
                if (this.SetBooleanValue(value))
                {
                    break;
                }

                this.SetStringValue(value);
                break;
            case DataType.String:
            default:
                this.SetStringValue(value);
                break;
        }
    }
}

To reproduce: run the attached sample project. Type "res" in the search box very very fast. You will notice that the results with starting with "re" are highlighted. 

Note: it is usually reproducible the first serahc after loading the form. 

To reproduce: set Excel-like filter according to the online documentation: https://docs.telerik.com/devtools/winforms/gridview/filtering/setting-filters-programmatically-(composite-descriptors)

            this.radGridView1.DataSource = this.productsBindingSource;
            this.productsTableAdapter.Fill(this.nwindDataSet.Products);

            this.radGridView1.EnableFiltering = true;
            this.radGridView1.ShowHeaderCellButtons = true;
            
            var filterDescriptor = new FilterDescriptor();
            filterDescriptor.PropertyName = "UnitsInStock";
            filterDescriptor.Value = 101;
            filterDescriptor.Operator = FilterOperator.IsEqualTo;

            var filterDescriptor2 = new FilterDescriptor();
            filterDescriptor2.PropertyName = "UnitsInStock";
            filterDescriptor2.Value = 104;
            filterDescriptor2.Operator = FilterOperator.IsEqualTo;
            var cfd = new CompositeFilterDescriptor();
            cfd.LogicalOperator = FilterLogicalOperator.Or;
            cfd.FilterDescriptors.Add(filterDescriptor);
            cfd.FilterDescriptors.Add(filterDescriptor2);
            cfd.IsFilterEditor = true;
            this.radGridView1.FilterDescriptors.Add(cfd);
            this.radGridView1.MasterTemplate.ExcelFilteredColumns.Add(this.radGridView1.Columns["UnitsInStock"]);

You will notice that the filter popup contains all possible values for this column which is OK, but none of the nodes is checked. It is necessary the visible rows to be checked. 

Workaround: check the nodes programmatically when the popup is shown:

        private void radGridView1_FilterPopupInitialized(object sender, Telerik.WinControls.UI.FilterPopupInitializedEventArgs e)
        {
            RadListFilterPopup popup = e.FilterPopup as RadListFilterPopup;
            if (popup!=null)
            {
                popup.Tag = e.Column.Name;
               popup.PopupOpened-=popup_PopupOpened;
                popup.PopupOpened+=popup_PopupOpened;
            }
        }

        private void popup_PopupOpened(object sender, EventArgs args)
        {
           RadListFilterPopup popup = sender as RadListFilterPopup;

           foreach (GridViewRowInfo row in this.radGridView1.ChildRows)
           {
             RadTreeNode node=   popup.MenuTreeElement.TreeView.FindNodes(row.Cells[popup.Tag+""].Value.ToString()).FirstOrDefault();
             if (node!=null)
             {
                 node.Checked = true;
             }
           }
        }

To reproduce: add a grid and a button and use the following code snippet:

[WORKAROUND: call Application.DoEvent at the beginning of the BindGrid method before rebinding]

   public partial class Form1 : Form
    {
        DataTable dtLeg;
        DataTable dtComp;
        DataTable dtClass;
        Int32 intClickCount = 0;
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            try
            {
                BindTables();
            }
            catch(Exception)
            {
                throw;
            }


        }

        private void BindTables()
        {
            try
            {
                dtLeg = new DataTable();
                dtComp = new DataTable();
                dtClass = new DataTable();

                Random rand1 = new Random();
                Random rand2 = new Random();
                Random rand3 = new Random();
                Random rand4 = new Random();

                int cNo = rand1.Next(2000, 10000);
                int dID = rand2.Next(2000, 10000);
                int dDetID = rand3.Next(2000, 10000);
                int depCode = rand4.Next(1000, 8000);
                string cCls = "Leg MIAGCM " + depCode.ToString();


                dtLeg.Columns.Add("Case_Number"); dtLeg.Columns.Add("Departure_Detail_Id"); dtLeg.Columns.Add("Departure_Id"); dtLeg.Columns.Add("Cabin_Class"); dtLeg.Columns.Add("Leg_Segment_type"); dtLeg.Columns.Add("Departure_Detail_Capture_Id");
                dtLeg.Columns.Add("DDC_Compartment_Id"); dtLeg.Columns.Add("Compartment_Structure_Id"); dtLeg.Columns.Add("Compartment_Name"); dtLeg.Columns.Add("Compartment_id"); dtLeg.Columns.Add("DDC_Class_Id"); dtLeg.Columns.Add("Class_Structure_Id");
                dtLeg.Columns.Add("Class_Name"); dtLeg.Columns.Add("Class_id"); dtLeg.Columns.Add("DDC_Subclass_Id"); dtLeg.Columns.Add("Subclass_Structure_Id"); dtLeg.Columns.Add("Subclass_Name"); dtLeg.Columns.Add("Subclass_id");
                dtLeg.Columns.Add("Adjusted_Authorizations"); dtLeg.Columns.Add("Adjusted_Availability"); dtLeg.Columns.Add("Adjusted_Bid_Price"); dtLeg.Columns.Add("Adjusted_Boardings"); dtLeg.Columns.Add("Adjusted_Bookings"); dtLeg.Columns.Add("Adjusted_Load_Factor");
                dtLeg.Columns.Add("Adjusted_Physical_Load_Factor"); dtLeg.Columns.Add("Adjusted_Revenue_Gain"); dtLeg.Columns.Add("Adjusted_SCI"); dtLeg.Columns.Add("Authorized_Capacity"); dtLeg.Columns.Add("Average_Fare_Value"); dtLeg.Columns.Add("Booked_Costs");
                dtLeg.Columns.Add("Booked_Revenue"); dtLeg.Columns.Add("Class_Usage_Ratio"); dtLeg.Columns.Add("Confidence"); dtLeg.Columns.Add("Current_Authorizations"); dtLeg.Columns.Add("Current_Availability"); dtLeg.Columns.Add("Current_Bookings");
                dtLeg.Columns.Add("Current_SCI"); dtLeg.Columns.Add("Go_Shows"); dtLeg.Columns.Add("Group_Bookings"); dtLeg.Columns.Add("Group_No_Show_Percentage"); dtLeg.Columns.Add("Limit_Compartment"); dtLeg.Columns.Add("Max_Constraint_Type");
                dtLeg.Columns.Add("Maximum_Authorizations_Constraint"); dtLeg.Columns.Add("Maximum_Leg_Authorization"); dtLeg.Columns.Add("Min_Constraint_Type"); dtLeg.Columns.Add("Minimum_Authorizations_Constraint"); dtLeg.Columns.Add("No_Show_Percentage"); dtLeg.Columns.Add("No_Shows");
                dtLeg.Columns.Add("Overbooking_Amount"); dtLeg.Columns.Add("Overbooking_Cost"); dtLeg.Columns.Add("Physical_Capacity"); dtLeg.Columns.Add("Projected_Authorized_Load_Factor"); dtLeg.Columns.Add("Projected_Boardings"); dtLeg.Columns.Add("Projected_Bookings");
                dtLeg.Columns.Add("Projected_Physical_Load_Factor"); dtLeg.Columns.Add("Projected_Revenue"); dtLeg.Columns.Add("Recommended_Authorized_Load_Factor"); dtLeg.Columns.Add("Recommended_Authorizations"); dtLeg.Columns.Add("Recommended_Availability"); dtLeg.Columns.Add("Recommended_Bid_Price");
                dtLeg.Columns.Add("Recommended_Boardings"); dtLeg.Columns.Add("Recommended_Bookings"); dtLeg.Columns.Add("Recommended_Physical_Load_Factor"); dtLeg.Columns.Add("Recommended_Revenue"); dtLeg.Columns.Add("Recommended_Revenue_Gain"); dtLeg.Columns.Add("Recommended_SCI");
                dtLeg.Columns.Add("Remaining_Cancellations"); dtLeg.Columns.Add("Original_Demand"); dtLeg.Columns.Add("Remaining_Demand"); dtLeg.Columns.Add("Revenue_Target"); dtLeg.Columns.Add("Standard_Deviation"); dtLeg.Columns.Add("Theoretical_Capacity");
                dtLeg.Columns.Add("Total_Booked_Costs"); dtLeg.Columns.Add("Total_Booked_Revenue"); dtLeg.Columns.Add("Total_Group_Bookings"); dtLeg.Columns.Add("Total_Projected_Demand"); dtLeg.Columns.Add("Total_Waitlist"); dtLeg.Columns.Add("Unit_Target");
                dtLeg.Columns.Add("Upsell_Adjusted_Demand"); dtLeg.Columns.Add("Upsell_Authorizations"); dtLeg.Columns.Add("Upsell_Availability"); dtLeg.Columns.Add("Upsell_Boardings"); dtLeg.Columns.Add("Upsell_Bookings"); dtLeg.Columns.Add("Upsell_Probability");
                dtLeg.Columns.Add("Upsell_Revenue"); dtLeg.Columns.Add("Upsell_Revenue_Gain"); dtLeg.Columns.Add("Upsell_SCI"); dtLeg.Columns.Add("Upsell_Remaining_Demand"); dtLeg.Columns.Add("Usage_Ratio"); dtLeg.Columns.Add("Waitlist");
                dtLeg.Columns.Add("Limit_Class"); dtLeg.Columns.Add("rec_limit"); dtLeg.Columns.Add("curr_limit"); dtLeg.Columns.Add("App_Capacity"); dtLeg.Columns.Add("Rec_Capacity"); dtLeg.Columns.Add("Is_Summary");
                dtLeg.Columns.Add("Current_Resource_Limit1"); dtLeg.Columns.Add("Recommand_Resource_Limit1"); dtLeg.Columns.Add("Upsell_Resource_limit1"); dtLeg.Columns.Add("Adjusted_Resource_limit1"); dtLeg.Columns.Add("Current_Resource_Limit2"); dtLeg.Columns.Add("Recommand_Resource_Limit2");
                dtLeg.Columns.Add("Upsell_Resource_limit2"); dtLeg.Columns.Add("Adjusted_Resource_limit2"); dtLeg.Columns.Add("Include_In_Total_Flag"); dtLeg.Columns.Add("Keep_Curr_Auth"); dtLeg.Columns.Add("Discrete_Recomended_Authorization"); dtLeg.Columns.Add("Discrete_Upsell_Authorization");
                dtLeg.Columns.Add("Nesting_Type"); dtLeg.Columns.Add("BookingPickup_DaysPrior_i"); dtLeg.Columns.Add("BookingPickup_Per_DaysPrior_i"); dtLeg.Columns.Add("BookingPickup_DaysPrior_j"); dtLeg.Columns.Add("BookingPickup_Per_DaysPrior_j"); dtLeg.Columns.Add("BookingPickup_DaysPrior_k");
                dtLeg.Columns.Add("BookingPickup_Per_DaysPrior_k"); dtLeg.Columns.Add("SDL_Booked"); dtLeg.Columns.Add("SDL_Booked_Percentage"); dtLeg.Columns.Add("Travelled_Bookings"); dtLeg.Columns.Add("Travelled_Bookings_Percentage"); dtLeg.Columns.Add("PE_Authorization");
                dtLeg.Columns.Add("PE_Availability"); dtLeg.Columns.Add("PE_Booking"); dtLeg.Columns.Add("PE_Boarding"); dtLeg.Columns.Add("PE_Revenue"); dtLeg.Columns.Add("PE_Revenue_Gain"); dtLeg.Columns.Add("Marginal_Fare");
                dtLeg.Columns.Add("Marginal_Demand"); dtLeg.Columns.Add("Price_Elasticity"); dtLeg.Columns.Add("PE_Group_ID"); dtLeg.Columns.Add("PE_Demand"); dtLeg.Columns.Add("Max_Alloc_Hus"); dtLeg.Columns.Add("PAX_Buffer_Hus");
                dtLeg.Columns.Add("PAX_Buffer_Hus_Type"); dtLeg.Columns.Add("Max_Alloc_Berths"); dtLeg.Columns.Add("PAX_Buffer_Berths"); dtLeg.Columns.Add("PAX_Buffer_Berths_Type"); dtLeg.Columns.Add("IS_Sent"); dtLeg.Columns.Add("StepType");
                dtLeg.Columns.Add("Adjusted_Authorizations_Calc"); dtLeg.Columns.Add("SDL_BP_DP_i"); dtLeg.Columns.Add("SDL_BP_DP_j"); dtLeg.Columns.Add("SDL_BP_DP_k"); dtLeg.Columns.Add("current_revenue"); dtLeg.Columns.Add("revenue_SDL");
                dtLeg.Columns.Add("Diff_Bkd_LY"); dtLeg.Columns.Add("Diff_Bkd_SDL"); dtLeg.Columns.Add("Diff_Revenue"); dtLeg.Columns.Add("Max_Booked");

                DataRow drLeg = dtLeg.NewRow();
                drLeg["Case_Number"] = cNo; drLeg["Departure_Detail_Id"] = dDetID; drLeg["Departure_Id"] = dID; drLeg["Cabin_Class"] = cCls; drLeg["Leg_Segment_type"] = "Leg"; drLeg["Departure_Detail_Capture_Id"] = "43824017"; drLeg["DDC_Compartment_Id"] = System.DBNull.Value;
                drLeg["Compartment_Structure_Id"] = System.DBNull.Value; drLeg["Compartment_Name"] = System.DBNull.Value;


                dtLeg.Rows.Add(drLeg);


                dtComp.Columns.Add("Case_Number"); dtComp.Columns.Add("Departure_Detail_Id"); dtComp.Columns.Add("Departure_Id"); dtComp.Columns.Add("Cabin_Class"); dtComp.Columns.Add("Leg_Segment_type"); dtComp.Columns.Add("Departure_Detail_Capture_Id");
                dtComp.Columns.Add("DDC_Compartment_Id"); dtComp.Columns.Add("Compartment_Structure_Id"); dtComp.Columns.Add("Compartment_Name"); dtComp.Columns.Add("Compartment_id"); dtComp.Columns.Add("DDC_Class_Id"); dtComp.Columns.Add("Class_Structure_Id");
                dtComp.Columns.Add("Class_Name"); dtComp.Columns.Add("Class_id"); dtComp.Columns.Add("DDC_Subclass_Id"); dtComp.Columns.Add("Subclass_Structure_Id"); dtComp.Columns.Add("Subclass_Name"); dtComp.Columns.Add("Subclass_id");
                dtComp.Columns.Add("Adjusted_Authorizations"); dtComp.Columns.Add("Adjusted_Availability"); dtComp.Columns.Add("Adjusted_Bid_Price"); dtComp.Columns.Add("Adjusted_Boardings"); dtComp.Columns.Add("Adjusted_Bookings"); dtComp.Columns.Add("Adjusted_Load_Factor");
                dtComp.Columns.Add("Adjusted_Physical_Load_Factor"); dtComp.Columns.Add("Adjusted_Revenue"); dtComp.Columns.Add("Adjusted_Revenue_Gain"); dtComp.Columns.Add("Adjusted_SCI"); dtComp.Columns.Add("Authorized_Capacity"); dtComp.Columns.Add("Average_Fare_Value"); dtComp.Columns.Add("Booked_Costs");
                dtComp.Columns.Add("Booked_Revenue"); dtComp.Columns.Add("Class_Usage_Ratio"); dtComp.Columns.Add("Confidence"); dtComp.Columns.Add("Current_Authorizations"); dtComp.Columns.Add("Current_Availability"); dtComp.Columns.Add("Current_Bookings");
                dtComp.Columns.Add("Current_SCI"); dtComp.Columns.Add("Go_Shows"); dtComp.Columns.Add("Group_Bookings"); dtComp.Columns.Add("Group_No_Show_Percentage"); dtComp.Columns.Add("Limit_Compartment"); dtComp.Columns.Add("Max_Constraint_Type");
                dtComp.Columns.Add("Maximum_Authorizations_Constraint"); dtComp.Columns.Add("Maximum_Leg_Authorization"); dtComp.Columns.Add("Min_Constraint_Type"); dtComp.Columns.Add("Minimum_Authorizations_Constraint"); dtComp.Columns.Add("No_Show_Percentage"); dtComp.Columns.Add("No_Shows");
                dtComp.Columns.Add("Overbooking_Amount"); dtComp.Columns.Add("Overbooking_Cost"); dtComp.Columns.Add("Physical_Capacity"); dtComp.Columns.Add("Projected_Authorized_Load_Factor"); dtComp.Columns.Add("Projected_Boardings"); dtComp.Columns.Add("Projected_Bookings");
                dtComp.Columns.Add("Projected_Physical_Load_Factor"); dtComp.Columns.Add("Projected_Revenue"); dtComp.Columns.Add("Recommended_Authorized_Load_Factor"); dtComp.Columns.Add("Recommended_Authorizations"); dtComp.Columns.Add("Recommended_Availability"); dtComp.Columns.Add("Recommended_Bid_Price");
                dtComp.Columns.Add("Recommended_Boardings"); dtComp.Columns.Add("Recommended_Bookings"); dtComp.Columns.Add("Recommended_Physical_Load_Factor"); dtComp.Columns.Add("Recommended_Revenue"); dtComp.Columns.Add("Recommended_Revenue_Gain"); dtComp.Columns.Add("Recommended_SCI");
                dtComp.Columns.Add("Remaining_Cancellations"); dtComp.Columns.Add("Original_Demand"); dtComp.Columns.Add("Remaining_Demand"); dtComp.Columns.Add("Revenue_Target"); dtComp.Columns.Add("Standard_Deviation"); dtComp.Columns.Add("Theoretical_Capacity");
                dtComp.Columns.Add("Total_Booked_Costs"); dtComp.Columns.Add("Total_Booked_Revenue"); dtComp.Columns.Add("Total_Group_Bookings"); dtComp.Columns.Add("Total_Projected_Demand"); dtComp.Columns.Add("Total_Waitlist"); dtComp.Columns.Add("Unit_Target");
                dtComp.Columns.Add("Upsell_Adjusted_Demand"); dtComp.Columns.Add("Upsell_Authorizations"); dtComp.Columns.Add("Upsell_Availability"); dtComp.Columns.Add("Upsell_Boardings"); dtComp.Columns.Add("Upsell_Bookings"); dtComp.Columns.Add("Upsell_Probability");
                dtComp.Columns.Add("Upsell_Revenue"); dtComp.Columns.Add("Upsell_Revenue_Gain"); dtComp.Columns.Add("Upsell_SCI"); dtComp.Columns.Add("Upsell_Remaining_Demand"); dtComp.Columns.Add("Usage_Ratio"); dtComp.Columns.Add("Waitlist");
                dtComp.Columns.Add("Limit_Class"); dtComp.Columns.Add("rec_limit"); dtComp.Columns.Add("curr_limit"); dtComp.Columns.Add("App_Capacity"); dtComp.Columns.Add("Rec_Capacity"); dtComp.Columns.Add("Is_Summary");
                dtComp.Columns.Add("Current_Resource_Limit1"); dtComp.Columns.Add("Recommand_Resource_Limit1"); dtComp.Columns.Add("Upsell_Resource_limit1"); dtComp.Columns.Add("Adjusted_Resource_limit1"); dtComp.Columns.Add("Current_Resource_Limit2"); dtComp.Columns.Add("Recommand_Resource_Limit2");
                dtComp.Columns.Add("Upsell_Resource_limit2"); dtComp.Columns.Add("Adjusted_Resource_limit2"); dtComp.Columns.Add("Include_In_Total_Flag"); dtComp.Columns.Add("Keep_Curr_Auth"); dtComp.Columns.Add("Discrete_Recomended_Authorization"); dtComp.Columns.Add("Discrete_Upsell_Authorization");
                dtComp.Columns.Add("Nesting_Type"); dtComp.Columns.Add("BookingPickup_DaysPrior_i"); dtComp.Columns.Add("BookingPickup_Per_DaysPrior_i"); dtComp.Columns.Add("BookingPickup_DaysPrior_j"); dtComp.Columns.Add("BookingPickup_Per_DaysPrior_j"); dtComp.Columns.Add("BookingPickup_DaysPrior_k");
                dtComp.Columns.Add("BookingPickup_Per_DaysPrior_k"); dtComp.Columns.Add("SDL_Booked"); dtComp.Columns.Add("SDL_Booked_Percentage"); dtComp.Columns.Add("Travelled_Bookings"); dtComp.Columns.Add("Travelled_Bookings_Percentage"); dtComp.Columns.Add("PE_Authorization");
                dtComp.Columns.Add("PE_Availability"); dtComp.Columns.Add("PE_Booking"); dtComp.Columns.Add("PE_Boarding"); dtComp.Columns.Add("PE_Revenue"); dtComp.Columns.Add("PE_Revenue_Gain"); dtComp.Columns.Add("Marginal_Fare");
                dtComp.Columns.Add("Marginal_Demand"); dtComp.Columns.Add("Price_Elasticity"); dtComp.Columns.Add("PE_Group_ID"); dtComp.Columns.Add("PE_Demand"); dtComp.Columns.Add("Max_Alloc_Hus"); dtComp.Columns.Add("PAX_Buffer_Hus");
                dtComp.Columns.Add("PAX_Buffer_Hus_Type"); dtComp.Columns.Add("Max_Alloc_Berths"); dtComp.Columns.Add("PAX_Buffer_Berths"); dtComp.Columns.Add("PAX_Buffer_Berths_Type"); dtComp.Columns.Add("IS_Sent"); dtComp.Columns.Add("StepType");
                dtComp.Columns.Add("Adjusted_Authorizations_Calc"); dtComp.Columns.Add("SDL_BP_DP_i"); dtComp.Columns.Add("SDL_BP_DP_j"); dtComp.Columns.Add("SDL_BP_DP_k"); dtComp.Columns.Add("current_revenue"); dtComp.Columns.Add("revenue_SDL");
                dtComp.Columns.Add("Diff_Bkd_LY"); dtComp.Columns.Add("Diff_Bkd_SDL"); dtComp.Columns.Add("Diff_Revenue"); dtComp.Columns.Add("Max_Booked"); dtComp.Columns.Add("COMPARTMENT_STRUCTURE_COMPARTMENT_ORDER");

               

                DataRow drComp = dtComp.NewRow();
                drComp["Case_Number"] = cNo; drComp["Departure_Detail_Id"] = dDetID; drComp["Departure_Id"] = dID; drComp["Cabin_Class"] = cCls; drComp["Leg_Segment_type"] = "Leg"; drComp["Departure_Detail_Capture_Id"] = "43824017"; drComp["DDC_Compartment_Id"] = "60513359";
                drComp["Compartment_Structure_Id"] = 4; drComp["Compartment_Name"] = "J"; drComp["Compartment_id"] = 1; drComp["Adjusted_Authorizations"] = 8; drComp["Adjusted_Availability"] = 7; drComp["Adjusted_Boardings"] = 1; drComp["Adjusted_Bookings"] = 1;
                drComp["Adjusted_Load_Factor"] = 0; drComp["Adjusted_Revenue"] = 349; drComp["Current_Authorizations"] = 8; drComp["Current_Availability"] = 7;

                dtComp.Rows.Add(drComp);

                DataRow drComp1 = dtComp.NewRow();
                drComp1["Case_Number"] = cNo; drComp1["Departure_Detail_Id"] = dDetID; drComp1["Departure_Id"] = dID; drComp1["Cabin_Class"] = cCls; drComp1["Leg_Segment_type"] = "Leg"; drComp1["Departure_Detail_Capture_Id"] = "43824017"; drComp1["DDC_Compartment_Id"] = "60513360";
                drComp1["Compartment_Structure_Id"] = 5; drComp1["Compartment_Name"] = "Y"; drComp1["Compartment_id"] = 2; drComp1["Adjusted_Authorizations"] = 114; drComp1["Adjusted_Availability"] = 97; drComp1["Adjusted_Boardings"] = 39; drComp1["Adjusted_Bookings"] = 39;
                drComp1["Adjusted_Load_Factor"] = 0; drComp1["Adjusted_Revenue"] = 350; drComp1["Current_Authorizations"] = 10; drComp1["Current_Availability"] = 10;

                dtComp.Rows.Add(drComp1);

                dtClass.Columns.Add("Case_Number"); dtClass.Columns.Add("Departure_Detail_Id"); dtClass.Columns.Add("Departure_Id"); dtClass.Columns.Add("Cabin_Class"); dtClass.Columns.Add("Leg_Segment_type"); dtClass.Columns.Add("Departure_Detail_Capture_Id");
                dtClass.Columns.Add("DDC_Compartment_Id"); dtClass.Columns.Add("Compartment_Structure_Id"); dtClass.Columns.Add("Compartment_Name"); dtClass.Columns.Add("Compartment_id"); dtClass.Columns.Add("DDC_Class_Id"); dtClass.Columns.Add("Class_Structure_Id");
                dtClass.Columns.Add("Class_Name"); dtClass.Columns.Add("Class_id"); dtClass.Columns.Add("DDC_Subclass_Id"); dtClass.Columns.Add("Subclass_Structure_Id"); dtClass.Columns.Add("Subclass_Name"); dtClass.Columns.Add("Subclass_id");
                dtClass.Columns.Add("Adjusted_Authorizations"); dtClass.Columns.Add("Adjusted_Availability"); dtClass.Columns.Add("Adjusted_Bid_Price"); dtClass.Columns.Add("Adjusted_Boardings"); dtClass.Columns.Add("Adjusted_Bookings"); dtClass.Columns.Add("Adjusted_Load_Factor");
                dtClass.Columns.Add("Adjusted_Physical_Load_Factor"); dtClass.Columns.Add("Adjusted_Revenue"); dtClass.Columns.Add("Adjusted_Revenue_Gain"); dtClass.Columns.Add("Adjusted_SCI"); dtClass.Columns.Add("Authorized_Capacity"); dtClass.Columns.Add("Average_Fare_Value"); dtClass.Columns.Add("Booked_Costs");
                dtClass.Columns.Add("Booked_Revenue"); dtClass.Columns.Add("Class_Usage_Ratio"); dtClass.Columns.Add("Confidence"); dtClass.Columns.Add("Current_Authorizations"); dtClass.Columns.Add("Current_Availability"); dtClass.Columns.Add("Current_Bookings");
                dtClass.Columns.Add("Current_SCI"); dtClass.Columns.Add("Go_Shows"); dtClass.Columns.Add("Group_Bookings"); dtClass.Columns.Add("Group_No_Show_Percentage"); dtClass.Columns.Add("Limit_Compartment"); dtClass.Columns.Add("Max_Constraint_Type");
                dtClass.Columns.Add("Maximum_Authorizations_Constraint"); dtClass.Columns.Add("Maximum_Leg_Authorization"); dtClass.Columns.Add("Min_Constraint_Type"); dtClass.Columns.Add("Minimum_Authorizations_Constraint"); dtClass.Columns.Add("No_Show_Percentage"); dtClass.Columns.Add("No_Shows");
                dtClass.Columns.Add("Overbooking_Amount"); dtClass.Columns.Add("Overbooking_Cost"); dtClass.Columns.Add("Physical_Capacity"); dtClass.Columns.Add("Projected_Authorized_Load_Factor"); dtClass.Columns.Add("Projected_Boardings"); dtClass.Columns.Add("Projected_Bookings");
                dtClass.Columns.Add("Projected_Physical_Load_Factor"); dtClass.Columns.Add("Projected_Revenue"); dtClass.Columns.Add("Recommended_Authorized_Load_Factor"); dtClass.Columns.Add("Recommended_Authorizations"); dtClass.Columns.Add("Recommended_Availability"); dtClass.Columns.Add("Recommended_Bid_Price");
                dtClass.Columns.Add("Recommended_Boardings"); dtClass.Columns.Add("Recommended_Bookings"); dtClass.Columns.Add("Recommended_Physical_Load_Factor"); dtClass.Columns.Add("Recommended_Revenue"); dtClass.Columns.Add("Recommended_Revenue_Gain"); dtClass.Columns.Add("Recommended_SCI");
                dtClass.Columns.Add("Remaining_Cancellations"); dtClass.Columns.Add("Original_Demand"); dtClass.Columns.Add("Remaining_Demand"); dtClass.Columns.Add("Revenue_Target"); dtClass.Columns.Add("Standard_Deviation"); dtClass.Columns.Add("Theoretical_Capacity");
                dtClass.Columns.Add("Total_Booked_Costs"); dtClass.Columns.Add("Total_Booked_Revenue"); dtClass.Columns.Add("Total_Group_Bookings"); dtClass.Columns.Add("Total_Projected_Demand"); dtClass.Columns.Add("Total_Waitlist"); dtClass.Columns.Add("Unit_Target");
                dtClass.Columns.Add("Upsell_Adjusted_Demand"); dtClass.Columns.Add("Upsell_Authorizations"); dtClass.Columns.Add("Upsell_Availability"); dtClass.Columns.Add("Upsell_Boardings"); dtClass.Columns.Add("Upsell_Bookings"); dtClass.Columns.Add("Upsell_Probability");
                dtClass.Columns.Add("Upsell_Revenue"); dtClass.Columns.Add("Upsell_Revenue_Gain"); dtClass.Columns.Add("Upsell_SCI"); dtClass.Columns.Add("Upsell_Remaining_Demand"); dtClass.Columns.Add("Usage_Ratio"); dtClass.Columns.Add("Waitlist");
                dtClass.Columns.Add("Limit_Class"); dtClass.Columns.Add("rec_limit"); dtClass.Columns.Add("curr_limit"); dtClass.Columns.Add("App_Capacity"); dtClass.Columns.Add("Rec_Capacity"); dtClass.Columns.Add("Is_Summary");
                dtClass.Columns.Add("Current_Resource_Limit1"); dtClass.Columns.Add("Recommand_Resource_Limit1"); dtClass.Columns.Add("Upsell_Resource_limit1"); dtClass.Columns.Add("Adjusted_Resource_limit1"); dtClass.Columns.Add("Current_Resource_Limit2"); dtClass.Columns.Add("Recommand_Resource_Limit2");
                dtClass.Columns.Add("Upsell_Resource_limit2"); dtClass.Columns.Add("Adjusted_Resource_limit2"); dtClass.Columns.Add("Include_In_Total_Flag"); dtClass.Columns.Add("Keep_Curr_Auth"); dtClass.Columns.Add("Discrete_Recomended_Authorization"); dtClass.Columns.Add("Discrete_Upsell_Authorization");
                dtClass.Columns.Add("Nesting_Type"); dtClass.Columns.Add("BookingPickup_DaysPrior_i"); dtClass.Columns.Add("BookingPickup_Per_DaysPrior_i"); dtClass.Columns.Add("BookingPickup_DaysPrior_j"); dtClass.Columns.Add("BookingPickup_Per_DaysPrior_j"); dtClass.Columns.Add("BookingPickup_DaysPrior_k");
                dtClass.Columns.Add("BookingPickup_Per_DaysPrior_k"); dtClass.Columns.Add("SDL_Booked"); dtClass.Columns.Add("SDL_Booked_Percentage"); dtClass.Columns.Add("Travelled_Bookings"); dtClass.Columns.Add("Travelled_Bookings_Percentage"); dtClass.Columns.Add("PE_Authorization");
                dtClass.Columns.Add("PE_Availability"); dtClass.Columns.Add("PE_Booking"); dtClass.Columns.Add("PE_Boarding"); dtClass.Columns.Add("PE_Revenue"); dtClass.Columns.Add("PE_Revenue_Gain"); dtClass.Columns.Add("Marginal_Fare");
                dtClass.Columns.Add("Marginal_Demand"); dtClass.Columns.Add("Price_Elasticity"); dtClass.Columns.Add("PE_Group_ID"); dtClass.Columns.Add("PE_Demand"); dtClass.Columns.Add("Max_Alloc_Hus"); dtClass.Columns.Add("PAX_Buffer_Hus");
                dtClass.Columns.Add("PAX_Buffer_Hus_Type"); dtClass.Columns.Add("Max_Alloc_Berths"); dtClass.Columns.Add("PAX_Buffer_Berths"); dtClass.Columns.Add("PAX_Buffer_Berths_Type"); dtClass.Columns.Add("IS_Sent"); dtClass.Columns.Add("StepType");
                dtClass.Columns.Add("Adjusted_Authorizations_Calc"); dtClass.Columns.Add("SDL_BP_DP_i"); dtClass.Columns.Add("SDL_BP_DP_j"); dtClass.Columns.Add("SDL_BP_DP_k"); dtClass.Columns.Add("current_revenue"); dtClass.Columns.Add("revenue_SDL");
                dtClass.Columns.Add("Diff_Bkd_LY"); dtClass.Columns.Add("Diff_Bkd_SDL"); dtClass.Columns.Add("Diff_Revenue"); dtClass.Columns.Add("Max_Booked"); dtClass.Columns.Add("COMPARTMENT_STRUCTURE_COMPARTMENT_ORDER");


                DataRow drClass = dtClass.NewRow();
                drClass["Case_Number"] = cNo; drClass["Departure_Detail_Id"] = dDetID; drClass["Departure_Id"] = dID; drClass["Cabin_Class"] = cCls; drClass["Leg_Segment_type"] = "Leg"; drClass["Departure_Detail_Capture_Id"] = "43824017"; drClass["DDC_Compartment_Id"] = "60513360";
                drClass["Compartment_Structure_Id"] = 5; drClass["Compartment_Name"] = "Y"; drClass["Compartment_id"] = 2; drClass["DDC_Class_Id"] = "6022025"; drClass["Class_Structure_Id"] = 4;
                drClass["Class_Name"] = "Y"; drClass["Class_id"] = 4; drClass["Adjusted_Authorizations"] = 8; drClass["Adjusted_Availability"] = 7; drClass["Adjusted_Boardings"] = 1; drClass["Adjusted_Bookings"] = 1;
                drClass["Adjusted_Load_Factor"] = 0; drClass["Adjusted_Revenue"] = 349; drClass["Current_Authorizations"] = 8; drClass["Current_Availability"] = 7;

                dtClass.Rows.Add(drClass);

                DataRow drClass1 = dtClass.NewRow();
                drClass1["Case_Number"] = cNo; drClass1["Departure_Detail_Id"] = dDetID; drClass1["Departure_Id"] = dID; drClass1["Cabin_Class"] = cCls; drClass1["Leg_Segment_type"] = "Leg"; drClass1["Departure_Detail_Capture_Id"] = "43824017"; drClass1["DDC_Compartment_Id"] = "60513359";
                drClass1["Compartment_Structure_Id"] = 4; drClass1["Compartment_Name"] = "J"; drClass1["Compartment_id"] = 1; drClass1["DDC_Class_Id"] = "6022020"; drClass1["Class_Structure_Id"] = 1;
                drClass1["Class_Name"] = "J"; drClass1["Class_id"] = 1; drClass1["Adjusted_Authorizations"] = 8; drClass1["Adjusted_Availability"] = 7; drClass1["Adjusted_Boardings"] = 1; drClass1["Adjusted_Bookings"] = 1;
                drClass1["Adjusted_Load_Factor"] = 0; drClass1["Adjusted_Revenue"] = 349; drClass1["Current_Authorizations"] = 8; drClass1["Current_Availability"] = 7;

                dtClass.Rows.Add(drClass1);

                DataRow drClass2 = dtClass.NewRow();
                drClass2["Case_Number"] = cNo; drClass2["Departure_Detail_Id"] = dDetID; drClass2["Departure_Id"] = dID; drClass2["Cabin_Class"] = cCls; drClass2["Leg_Segment_type"] = "Leg"; drClass2["Departure_Detail_Capture_Id"] = "43824017"; drClass2["DDC_Compartment_Id"] = "60513359";
                drClass2["Compartment_Structure_Id"] = 4; drClass2["Compartment_Name"] = "J"; drClass2["Compartment_id"] = 1; drClass2["DDC_Class_Id"] = "6022020"; drClass2["Class_Structure_Id"] = 17;
                drClass2["Class_Name"] = "C"; drClass2["Class_id"] = 17; drClass2["Adjusted_Authorizations"] = 8; drClass2["Adjusted_Availability"] = 7; drClass2["Adjusted_Boardings"] = 1; drClass2["Adjusted_Bookings"] = 1;
                drClass2["Adjusted_Load_Factor"] = 0; drClass2["Adjusted_Revenue"] = 349; drClass2["Current_Authorizations"] = 8; drClass2["Current_Availability"] = 7;

                dtClass.Rows.Add(drClass2);


                BindGrid();
            }
            catch(Exception)
            {
                throw;
            }
        }

        private void BindGrid()
        {
            try
            {

                radGridWorksheet.MasterTemplate.Templates.Clear();
                radGridWorksheet.Relations.Clear();
                radGridWorksheet.DataSource = dtLeg;
                radGridWorksheet.AllowAddNewRow = false;
                radGridWorksheet.AllowDeleteRow = false;
                radGridWorksheet.AllowEditRow = true;
                radGridWorksheet.AutoGenerateColumns = true;
                radGridWorksheet.BestFitColumns();
                radGridWorksheet.GridViewElement.DrawBorder = false;
                radGridWorksheet.GridViewElement.GroupPanelElement.DrawBorder = false;

                GridViewTemplate childDetailCaptureDate = new GridViewTemplate();
                childDetailCaptureDate.Caption = "Leg";
                childDetailCaptureDate.Columns.Clear();
                childDetailCaptureDate.AllowAddNewRow = false;
                childDetailCaptureDate.AllowDeleteRow = false;
                childDetailCaptureDate.AllowEditRow = true;
                childDetailCaptureDate.AutoGenerateColumns = true;
                childDetailCaptureDate.BestFitColumns();
                childDetailCaptureDate.DataSource = dtComp;
                radGridWorksheet.MasterTemplate.Templates.Add(childDetailCaptureDate);
                GridViewRelation relationCaptureDate = new GridViewRelation(radGridWorksheet.MasterTemplate);
                relationCaptureDate.ChildTemplate = childDetailCaptureDate;
                relationCaptureDate.RelationName = "Capture";
                relationCaptureDate.ParentColumnNames.Add("Departure_Detail_Capture_Id");
                relationCaptureDate.ChildColumnNames.Add("Departure_Detail_Capture_Id");
                radGridWorksheet.Relations.Add(relationCaptureDate);

                GridViewTemplate childDetailCaptureDateComp = new GridViewTemplate();
                childDetailCaptureDateComp.Caption = "Comp";
                childDetailCaptureDateComp.Columns.Clear();
                childDetailCaptureDateComp.AllowAddNewRow = false;
                childDetailCaptureDateComp.AllowDeleteRow = false;
                childDetailCaptureDateComp.AllowEditRow = true;
                childDetailCaptureDateComp.AutoGenerateColumns = true;
                childDetailCaptureDateComp.BestFitColumns();
                childDetailCaptureDateComp.DataSource = dtClass;
                childDetailCaptureDate.Templates.Add(childDetailCaptureDateComp);
                GridViewRelation relationCaptureDateCompatment = new GridViewRelation(childDetailCaptureDate);
                relationCaptureDateCompatment.ChildTemplate = childDetailCaptureDateComp;
                relationCaptureDateCompatment.RelationName = "Compartment";
                relationCaptureDateCompatment.ParentColumnNames.Add("DDC_Compartment_Id");
                relationCaptureDateCompatment.ChildColumnNames.Add("DDC_Compartment_Id");
                radGridWorksheet.Relations.Add(relationCaptureDateCompatment); 

                radGridWorksheet.MasterTemplate.ExpandAll();

            }
            catch(Exception e0)
            { 
                MessageBox.Show(String.Format("{0}\n{1}", e0.Message, e0.StackTrace));
                throw;

            }
        }

        private void radButton1_Click(object sender, EventArgs e)
        {
            try
            {
                intClickCount = intClickCount + 1;
                //Thread.Sleep(1000);
                radButton1.Text = "Next Click " + intClickCount;
                BindTables();
            }
            catch(Exception e0)
            { 
                MessageBox.Show(String.Format("{0}\n{1}", e0.Message, e0.StackTrace));
                throw;

            }

        }
    }

Workaround: handle the SortChanging and FilterChanging events and clear the search criteria from the search row. The stored search string can later be restored in the SortChanged and FilterChanged events

string filter = string.Empty;
private void RadGrid_FilterChanged(object sender, GridViewCollectionChangedEventArgs e)
{
    this.radGrid.MasterView.TableSearchRow.Search(filter);
}

private void RadGrid_SortChanged(object sender, GridViewCollectionChangedEventArgs e)
{
    this.radGrid.MasterView.TableSearchRow.Search(filter);
}

private void RadGrid_SortChanging(object sender, GridViewCollectionChangingEventArgs e)
{
    this.filter = this.radGrid.MasterView.TableSearchRow.SearchCriteria;
    this.radGrid.MasterView.TableSearchRow.Search(null);
}

private void RadGrid_FilterChanging(object sender, GridViewCollectionChangingEventArgs e)
{
    this.filter = this.radGrid.MasterView.TableSearchRow.SearchCriteria;
    this.radGrid.MasterView.TableSearchRow.Search(null);
}

How to reproduce: 
public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();

        ThemeResolutionService.AllowAnimations = false;
        this.radGridView1.DataSource = this.GetData();
    }

    private DataTable GetData()
    {
        DataTable dt = new DataTable();
        dt.Columns.Add("Id", typeof(int));
        dt.Columns.Add("Name", typeof(string));
        dt.Rows.Add(1, "\u0002x09");
        for (int i = 1; i < 10; i++)
        {
            dt.Rows.Add(i, "name");
        }

        return dt;
    }

    private void radButton1_Click(object sender, EventArgs e)
    {
        GridViewSpreadExport spreadExporter = new GridViewSpreadExport(this.radGridView1);
        spreadExporter.FileExportMode = FileExportMode.CreateOrOverrideFile;
        SpreadExportRenderer exportRenderer = new SpreadExportRenderer();
        spreadExporter.RunExport(@"..\..\exported-file.xlsx", exportRenderer);
    }
}

ArgumentException with clarification similar to  "'\u001f', hexadecimal value 0x1F, is an invalid character." is thrown when trying to export document containing characters which are not supported in XML document - such as some control characters like 0x00, 0x1F, 0x1B, etc. Such characters are described in the XML specification here: https://www.w3.org/TR/xml/#charsets.

Although the escaped strings are not supported (see  https://feedback.telerik.com/Project/184/Feedback/Details/190228 ), the library could prevent the exception and export the document successfully by skipping such characters.

Workaround: remove such characters before the export. Check the following StackOverflow answer for some ideas on code for replacing the characters: http://stackoverflow.com/a/14323524/259206

A similar issue can be also observed in RadTreeView:

Workaround RadGridView: 
private void RadGridView1_CellEditorInitialized(object sender, GridViewCellEventArgs e)
{
    RadTextBoxEditor editor = e.ActiveEditor as RadTextBoxEditor;
    if (editor != null)
    {
        editor.EditorElement.MinSize = new Size(0, 30);
    }
}

Workaround RadTreeView:
 
private void RadTreeView1_EditorInitialized(object sender, TreeNodeEditorInitializedEventArgs e)
{
    TreeViewTextBoxEditor editor = e.Editor as TreeViewTextBoxEditor;
    if (editor != null)
    {
        ((BaseTextBoxEditorElement)editor.EditorElement).TextBoxItem.TextBoxControl.MinimumSize = new Size(0, 24);
    }
}

In 125% the RadTextBox in the Fluent theme keeps shrinking:

Workaround
public RadForm1()
{
    InitializeComponent();

    SizeF dpi = NativeMethods.GetMonitorDpi(Screen.PrimaryScreen, NativeMethods.DpiType.Effective);
    this.radTextBox1.MinimumSize = new Size(0, (int)(24 * dpi.Height));
}

To reproduce:
Use the following code
private void RadGridView1_UserAddingRow(object sender, GridViewRowCancelEventArgs e)
{
    radGridView1.MasterView.TableAddNewRow.CancelAddNewRow();
    radGridView1.MasterView.ViewTemplate.DataView.CurrentItem.IsCurrent = false;
}

Place the new row at the bottom. While in edit mode press tab to fill until an exception is thrown.

Workaround:
BaseGridBehavior gridBehavior = radGridView1.GridBehavior as BaseGridBehavior;
gridBehavior.UnregisterBehavior(typeof(GridViewNewRowInfo));
gridBehavior.RegisterBehavior(typeof(GridViewNewRowInfo), new CustomGridRowBehavior());


internal class CustomGridRowBehavior : GridNewRowBehavior
{
    protected override bool ProcessTabKey(KeyEventArgs keys)
    {
        bool newRowIsInEditMode = this.IsInEditMode && this.GridViewElement.CurrentRow is GridViewNewRowInfo;

        if ( newRowIsInEditMode  && this.GridViewElement.Navigator.IsLastEditableColumn(this.GridViewElement.CurrentColumn))              
        {
            this.GridViewElement.Navigator.SelectFirstColumn();

            while (this.GridViewElement.CurrentColumn.ReadOnly && this.GridViewElement.Navigator.SelectNextColumn())
            { }
            return false;
        }
        return base.ProcessTabKey(keys);
    }
}

To reproduce:
private void RadGridView1_UserAddingRow(object sender, Telerik.WinControls.UI.GridViewRowCancelEventArgs e)
{
    radGridView1.MasterView.TableAddNewRow.CancelAddNewRow();
}
See attached video.

Workaround:
private void RadGridView1_UserAddingRow(object sender, Telerik.WinControls.UI.GridViewRowCancelEventArgs e)
{
    radGridView1.MasterView.TableAddNewRow.CancelAddNewRow();
    radGridView1.MasterView.ViewTemplate.DataView.CurrentItem.IsCurrent = false;
}

To reproduce: 
            DataTable dt = new DataTable();
            dt.Columns.Add("Id", typeof(int));
            dt.Columns.Add("Name", typeof(string));
            dt.Columns.Add("NumberAsShort", typeof(ushort));
            for (int i = 0; i < 100; i++)
            {
                dt.Rows.Add(i, "Row" + i, i );
            }
            this.radGridView1.DataSource = dt;

Workaround: use the CellFormatting event https://docs.telerik.com/devtools/winforms/gridview/cells/formatting-cells

To reproduce, perform the following steps with the attached project:

Step 1: Create Sample Database
==============================
New (Sample1.db)
Import
Save
Close

Step 2:
======
Open (Sample1.db)
Import
Save
Close

Step 3:
======
New (Sample2.db)
Import (Exception)

Workaround:
 radGridView1.GridViewElement.Navigator = new MyNavigator();

class MyNavigator : BaseGridNavigator
{
    public override bool SelectLastRow()
    {
        var enumerator = typeof(BaseGridNavigator).GetField("enumerator", BindingFlags.NonPublic | BindingFlags.Instance).GetValue(this) as GridTraverser;
        enumerator.Reset();
      
        return base.SelectLastRow();
    }
}

Use attached to reproduce.

Workaround:

Use CellFormatting instead of RowFormating. 

Workaround: 

        private void radGridView1_CellFormatting(object sender, Telerik.WinControls.UI.CellFormattingEventArgs e)
        {
            GridDataCellElement cell = e.CellElement as GridDataCellElement ;
            if (cell!=null && cell.SelfReferenceLayout!=null)
            {

                foreach (RadElement item in cell.SelfReferenceLayout.StackLayoutElement.Children)
                {
                    if (!(item is GridTreeExpanderItem))
                    {
                        item.Visibility = ElementVisibility.Collapsed;
                    }
                    else
                    {
                        item.Visibility = ElementVisibility.Visible;
                    }
                } 
            } 
        }

Use attached to reproduce.

Workaround:

DragDropService.AllowAutoScrollColumnsWhileDragging = false;
DragDropService.AllowAutoScrollRowsWhileDragging = false;

Use attached to reproduce.

Workaround
- Set the position at runtime. 
   Me.radGridView1.MasterTemplate.AddNewRowPosition = Telerik.WinControls.UI.SystemRowPosition.Bottom

To reproduce: if you pin a calculator or a hyperlink column you will notice that the cells belonging to these columns remain white. However, the cells from other column types  have a light blue/gray fill color for pinned state. 

Workaround: 
private void RadGridView1_CellFormatting(object sender, CellFormattingEventArgs e)
{
    if (e.Column.IsPinned)
    {
        e.CellElement.BackColor = Color.FromArgb(235, 244, 252);
    }
    else
    {
        e.CellElement.ResetValue(LightVisualElement.BackColorProperty, ValueResetFlags.Local);
    }
}

To reproduce: please refer to the attached screenshot.

Workaround: add the FilterDescriptor programmatically: https://docs.telerik.com/devtools/winforms/gridview/filtering/setting-filters-programmatically-(simple-descriptors)