Please run the attached sample project and follow the steps from the attached gif file to replicate the visual glitch.

To reproduce: run the attached sample project. Select an item and press F2, select a new item from the drop-down. You will encounter an error because the ActiveEditor is now null in the ItemValueChanging event.

Workaround: in the EditorInitialized event you can subscribe to the RadDropDownListElement.SelectedIndexChanging event:

private void radListView1_EditorInitialized(object sender, ListViewItemEditorInitializedEventArgs e)
{
    ListViewDropDownListEditor editor = e.Editor as ListViewDropDownListEditor;
    if (editor==null)
    {
        return;
    }
    RadDropDownListElement dropdown = (RadDropDownListElement)editor.EditorElement;
    dropdown.SelectedIndexChanging-=dropdown_SelectedIndexChanging;
    dropdown.SelectedIndexChanging+=dropdown_SelectedIndexChanging;
}

I got an exception when I'll try to add new items in a radcheckeddropdownlist.
No differences between AddRange(List<objects>) and Add(<object>)

We use the dropdownlist in the CustomAppointmentEditDialog for resources and here some sample code:
                //cmbResourceMulti.BeginUpdate();
        
                cmbResourceMulti.Items.Clear();
                var resources = data.GetRooms();

                List<RadCheckedListDataItem> lst = new List<RadCheckedListDataItem>();

                foreach (var res in resources)
                {
                    var item = new RadCheckedListDataItem(res.Raumname);
                    item.Tag = res;
                    item.Value = res.ID;
                    lst.Add(item);

                    if (sourceEvent.ResourceId != null && sourceEvent.ResourceIds.Contains(new EventId(res.ID)))
                    {
                        item.Checked = true;
                    }
                }
                
                cmbResourceMulti.Items.AddRange(lst.ToArray());
                //cmbResourceMulti.EndUpdate();
                cmbResourceMulti.Refresh();

On first load everything is working fine. Open an existing appointment and check a new resource. After saving the appointment and reopen it, the error appears .
See attached file.

Can you help please?
 

To reproduce use the attached project.

Workaround:
radCheckedDropDownList1.CheckedDropDownListElement.BeginUpdate();

radCheckedDropDownList1.CheckedMember = "Selected";
radCheckedDropDownList1.DisplayMember = "Name";         
radCheckedDropDownList1.DataSource = dataSource;

radCheckedDropDownList1.CheckedDropDownListElement.EndUpdate();

How to reproduce: Bind RadCardView to the Employees table from the Northwind database:
public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();

        this.radCardView1.CardViewItemCreating += radCardView1_CardViewItemCreating;
    }

    private void radCardView1_CardViewItemCreating(object sender, Telerik.WinControls.UI.CardViewItemCreatingEventArgs e)
    {
        CardViewGroupItem group = e.NewItem as CardViewGroupItem;
        if (group != null)
        {
            group.IsExpanded = false;
        }
    }

    private void Form1_Load(object sender, EventArgs e)
    {
        this.employeesTableAdapter.Fill(this.nwindDataSet.Employees);
    }
}

Workaround: handle the CardViewItemFormatting event
private void radCardView1_CardViewItemFormatting(object sender, CardViewItemFormattingEventArgs e)
{
    CardViewGroupItem group = e.Item as CardViewGroupItem;
    if (group != null && group.Tag == null && group.Parent != null && group.Parent.Parent != null && group.Parent.Parent is CardListViewVisualItem)
    {
        group.IsExpanded = false;
        group.Tag = "Processed";
    }
}

Version Q3 2014 WinForms RadListView generates duplicate ItemMouseDoubleClick events when ViewType is set to DetailsView. 

See attached demo project.

Steps to reproduce.

1. Add a RadListView to a form and set its height to around 68.
2. Set the ViewType to ViewType.Details.
3. Add several items so the vertical scroll bar would show.
4. scroll to the bottom and use the scroll bar up button to scroll up.

You will see that only half of some items would be shown, until you reach the top.

Resolution: When available space for rows is less than the height of a single row is normal to not see the hole row. 

DECLINED: Data items must implement the INotifyPropertyChanged interface in order for the RadListView to be able to automatically reflect the changes. Here is how MyObject should be implemented:
    public class MyObject : INotifyPropertyChanged
    {
        private string name;

        public MyObject(string name)
        {
            this.name = name;
        }

        public string Name
        {
            get
            {
                return this.name;
            }
            set
            {
                this.name = value;
                if (this.PropertyChanged != null)
                {
                    this.PropertyChanged(this, new PropertyChangedEventArgs("Name"));
                }
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;
    }





Reproduce:
-add a RadListView and bind it to a BindingList
-add a RadButton and implement its Click event to modify an item in the BindingList
The expected behaviour is to see the RadListView visually updated, but only DataSource collection is updated. Refreshing the RadListView does not help.

Workaround:
public partial class Form1 : Form
    {
        BindingList<MyObject> bindingList;

        public Form1()
        {
            InitializeComponent();

            bindingList = new BindingList<MyObject>();
            bindingList.Add(new MyObject("Item1"));
            bindingList.Add(new MyObject("Item2"));
            bindingList.Add(new MyObject("Item3"));
            bindingList.Add(new MyObject("Item4"));

            this.radListView1.DataSource = bindingList;
            this.radListView1.DisplayMember = "Name";
        }

        private void radButton1_Click(object sender, EventArgs e)
        {
            if (this.radListView1.SelectedItem != null)
            {
                bindingList[1].Name = "NewName";
                
                foreach (var item in this.radListView1.ListViewElement.ViewElement.Children[0].Children)
                {
                    ((SimpleListViewVisualItem)item).Synchronize();
                }
            }
        }
    }

    public class MyObject 
    {
        private string name;

        public MyObject(string name)
        {
            this.name = name;
        }

        public string Name
        {
            get
            {
                return this.name;
            }
            set
            {
                this.name = value;
            }
        }
    }

Reason: this is the expected behavior.