To reproduce: add a RadMaskedEditBox and use the following code:

Sub New()

    InitializeComponent()

    Me.RadMaskedEditBox1.MaskType = Telerik.WinControls.UI.MaskType.Numeric
    Me.RadMaskedEditBox1.Mask = "N1"
        Dim item As Item = New Item(Nothing, "Item1")
    RadMaskedEditBox1.DataBindings.Add("Value", item, "StockTypeId", True, DataSourceUpdateMode.OnPropertyChanged)
End Sub

Public Class Item
    Private _stockId As Nullable(Of Integer)

    Public Sub New(value As Nullable(Of Integer), name As String)
        Me._stockId = value
    End Sub

    Public Property StockTypeId() As Nullable(Of Integer)
        Get
            Return _stockId
        End Get
        Set(ByVal value As Nullable(Of Integer))
            _stockId = value
            Console.WriteLine(value)
        End Set
    End Property
End Class

The user is not allowed to enter a new numeric value.

Wokraround:

Public Class CustomNumericCharacterTextBoxProvider
    Inherits NumericCharacterTextBoxProvider

    Private owner As RadMaskedEditBoxElement
    Public Sub New(mask As String, culture As CultureInfo, numericType As NumericCharacterTextBoxProvider.RadNumericMaskFormatType, _
    owner As RadMaskedEditBoxElement)
        MyBase.New(mask, culture, numericType, owner)
        Me.owner = owner
    End Sub
    Protected Overrides Function AllowAppendCharacters() As Boolean
        If owner.Text = "" AndAlso owner.Mask = "N1" Then
            Return True
        End If

        Return MyBase.AllowAppendCharacters()
    End Function
End Class

Public Class CustomMaskedEditBox
    Inherits RadMaskedEditBox

    Public Overrides Property ThemeClassName As String
        Get
            Return GetType(RadMaskedEditBox).FullName
        End Get
        Set(value As String)
            MyBase.ThemeClassName = value
        End Set
    End Property

    Public Sub New()
        MyBase.New()
        Me.MaskType = Telerik.WinControls.UI.MaskType.Numeric
        Me.Mask = "N1"
        Dim numericMaskProvider As NumericMaskTextBoxProvider = Me.MaskedEditBoxElement.Provider
        Dim fi As FieldInfo = GetType(NumericMaskTextBoxProvider).GetField("provider", BindingFlags.Instance Or BindingFlags.NonPublic)
        fi.SetValue(numericMaskProvider, _
                    New CustomNumericCharacterTextBoxProvider(numericMaskProvider.Mask, numericMaskProvider.Culture, _
                    NumericMaskTextBoxProvider.GetFormat(numericMaskProvider.Mask, numericMaskProvider.Culture), _
                    Me.MaskedEditBoxElement))

    End Sub
End Class

How to reproduce:
Check also the attached video

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }

    private void radButton1_Click(object sender, EventArgs e)
    {
        this.radAutoCompleteBox1.AutoCompleteItems.Clear();

        List<RadListDataItem> autoCompleteEntries = new List<RadListDataItem>();
        for (int i = 0; i < 10000; i++)
        {
            autoCompleteEntries.Add(new RadListDataItem("Joe Smith", "joe@fakecompany.com"));
            autoCompleteEntries.Add(new RadListDataItem("Adam Petersen", "adam@qwerty.com"));
            autoCompleteEntries.Add(new RadListDataItem("Jack Russel", "jack@russel.nocom"));
            autoCompleteEntries.Add(new RadListDataItem("Daniel Finger", "daniel.pinger@gmail.com"));
            autoCompleteEntries.Add(new RadListDataItem("Richard Vail", "rvail@richardvail.com"));
            autoCompleteEntries.Add(new RadListDataItem("Sebastian Jonnson", "s.jonnson@sjonnson.com"));
            autoCompleteEntries.Add(new RadListDataItem("Lee Cooper", "lee.cooper@coopercoorp.com"));
            autoCompleteEntries.Add(new RadListDataItem("Kelvin Clain", "kclain@clainkevin.com"));
            autoCompleteEntries.Add(new RadListDataItem("Maria Jenson", "mjenson@mariajenson.com"));
            autoCompleteEntries.Add(new RadListDataItem("Chelsea Maarten", "chelsea@maarten.com"));
        }

        this.radAutoCompleteBox1.AutoCompleteItems.AddRange(autoCompleteEntries);
    }
}

Workaround: use Begin/End update block and reset the private patternText field:
public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }

    private void radButton1_Click(object sender, EventArgs e)
    {
        typeof(RadTextBoxListElement).GetField("patternText", BindingFlags.Instance | BindingFlags.NonPublic).SetValue(this.radAutoCompleteBox1.ListElement, null);

        this.radAutoCompleteBox1.AutoCompleteItems.Clear();

        List<RadListDataItem> autoCompleteEntries = new List<RadListDataItem>();
        for (int i = 0; i < 10000; i++)
        {
            autoCompleteEntries.Add(new RadListDataItem("Joe Smith", "joe@fakecompany.com"));
            autoCompleteEntries.Add(new RadListDataItem("Adam Petersen", "adam@qwerty.com"));
            autoCompleteEntries.Add(new RadListDataItem("Jack Russel", "jack@russel.nocom"));
            autoCompleteEntries.Add(new RadListDataItem("Daniel Finger", "daniel.pinger@gmail.com"));
            autoCompleteEntries.Add(new RadListDataItem("Richard Vail", "rvail@richardvail.com"));
            autoCompleteEntries.Add(new RadListDataItem("Sebastian Jonnson", "s.jonnson@sjonnson.com"));
            autoCompleteEntries.Add(new RadListDataItem("Lee Cooper", "lee.cooper@coopercoorp.com"));
            autoCompleteEntries.Add(new RadListDataItem("Kelvin Clain", "kclain@clainkevin.com"));
            autoCompleteEntries.Add(new RadListDataItem("Maria Jenson", "mjenson@mariajenson.com"));
            autoCompleteEntries.Add(new RadListDataItem("Chelsea Maarten", "chelsea@maarten.com"));
        }

        this.radAutoCompleteBox1.ListElement.DataLayer.ListSource.BeginUpdate();
        this.radAutoCompleteBox1.AutoCompleteItems.AddRange(autoCompleteEntries);
        this.radAutoCompleteBox1.ListElement.DataLayer.ListSource.EndUpdate();
    }
}

Workaround:
this.radTextBox1.TextBoxElement.Fill.BackColor = backColor;
this.radTextBox1.TextBoxElement.BackColor = backColor;

To reproduce:
- Set the mask to IP.
- Change the culture to German.

Workaround:
Set the Culture of the RadMaskedEditBox to English.

To reproduce:

1. Add a RadForm and a RadTimePicker/RadDateTimePicker.
2. Change the Enabled property of the RadTimePicker/RadDateTimePicker to false at design time.
3. Apply the Office2013Light theme to the RadTimePicker/RadDateTimePicker at design time.
4. Apply the same theme to the RadForm at design time.

If you run the application, you will notice that RadTimePicker/RadDateTimePicker has a gray back color. However, if you turn on/off the Enabled property in a button's Click event, the back color is not gray.

Workaround: set the Enabled property to false in the Load event.

Please refer to the attached gif file demonstrating how to reproduce the problem.

Workaround: close the popup when pressing Backspace:

 this.radTextBox1.TextBoxElement.TextBoxItem.TextBoxControl.KeyDown+=TextBoxControl_KeyDown;
private void TextBoxControl_KeyDown(object sender, KeyEventArgs e)
{
    if (e.KeyData== Keys.Back)
    {
        TextBoxSpellChecker textBoxSpellChecker = _radSpellChecker.GetControlSpellChecker(typeof(RadTextBox)) as TextBoxSpellChecker;
        if (textBoxSpellChecker!=null)
        {
            textBoxSpellChecker.DropDownMenu.ClosePopup(RadPopupCloseReason.Keyboard);
        }
    }
}

To reproduce:
- Use the SpellCheck as you type functionality with RadTextBox.
- The "Ignore All" and "Add To Dictionary" strings in the context menu are not changed.

Workaround:
public RadForm1()
{
    InitializeComponent();
    radSpellChecker1.AutoSpellCheckControl = radTextBox1;
    TextBoxSpellChecker textBoxControlSpellChecker = this.radSpellChecker1.GetControlSpellChecker(typeof(RadTextBox)) as TextBoxSpellChecker;
    textBoxControlSpellChecker.DropDownMenu.DropDownOpened += DropDownMenu_DropDownOpened;
}

private void DropDownMenu_DropDownOpened(object sender, EventArgs e)
{
    var menu = (RadDropDownMenu)sender;

    foreach (var item in menu.Items)
    {
        if (item.Text == "Add To Dictionary")
        {
            item.Text = "test";
        }
        if (item.Text == "Ignore All")
        {
            item.Text = "test";
        }
    }
}

After binding a boolean property to RadDateTimePicker:Checked, changes made in the property reflect in the GUI, but changes made in the GUI even after lost focus are not reflected on the boolean property. The same test was done with winforms DateTimePicker and the expected behaviour was observed(not the situation reported). above). For further testing background, the class wich contains the binded boolean, implements INotifyPropertyChanged.

To reproduce:

public Form1()
{
    InitializeComponent();

    this.radTextBox1.Multiline = true;
    this.radTextBox1.Size = new Size(200, 200);
    this.radTextBox1.TextChanged += radTextBox1_TextChanged;
}

private void radTextBox1_TextChanged(object sender, EventArgs e)
{
    this.radTextBox1.BackColor = Color.Red;
}

Note: when you keep pressed a specific key, you will notice that the memory consumption is increased, although if you force the GarbageCollector, it is released. It is also noticeable that there is text lagging while typing. Please refer to the attached gif file.

Workaround:
            this.radTextBox1.TextBoxElement.TextBoxItem.TextBoxControl.BackColor = Color.Red;

To reproduce:
- Disable the control.
- The text box has a white background.

- Workaround:
Set the  back color of the RadTimeMaskedEditBoxElement in for the disabled state in Visual Style Builder. 

To reproduce:

public Form1()
{
    InitializeComponent();

    this.radDateTimePicker1.Culture  = new System.Globalization.CultureInfo("en-GB");
    RadTimePickerLocalizationProvider.CurrentProvider = new MyTimePickerLocalizationProvider();
    this.radDateTimePicker1.DateTimePickerElement.ShowTimePicker = true; 
} 

class MyTimePickerLocalizationProvider : RadTimePickerLocalizationProvider
{
    public override string GetLocalizedString(string id)
    {
        switch (id)
        {
            case RadTimePickerStringId.HourHeaderText:
                return "TEST Hours";
            case RadTimePickerStringId.MinutesHeaderText:
                return "TEST Minutes";
            case RadTimePickerStringId.CloseButtonText:
                return "TEST CLOSE";
            default:
                return string.Empty;
        }
    }
}

Workaround:
 RadDateTimePickerCalendar calendarBehaviorFrom = this.radDateTimePicker1.DateTimePickerElement.GetCurrentBehavior() as RadDateTimePickerCalendar;
 calendarBehaviorFrom.Calendar.ShowFooter = true;
 calendarBehaviorFrom.PopupControl.Opened += PopupControl_PopupOpened;

private void PopupControl_PopupOpened(object sender, EventArgs args)
        {
            RadDateTimePickerDropDown dd = sender as RadDateTimePickerDropDown;
            TimePickerDoneButtonContent buttonContent = ((RadPanel)dd.HostedControl).Controls[2] as TimePickerDoneButtonContent;
            var doneButton = ((Telerik.WinControls.UI.TimePickerDoneButtonElement)(buttonContent.RootElement.Children[0]));
            doneButton.ButtonElement.Text = RadTimePickerLocalizationProvider.CurrentProvider.GetLocalizedString(RadTimePickerStringId.CloseButtonText); 
        }

To reproduce: please refer to the attached gif file.

The error is applicable for all controls that use RadColorDialog while editing, e.g. RadGridView, RadPropertyGrid. 

Workaround: disable the spineditors:

private void RadPropertyGrid1_EditorInitialized(object sender, Telerik.WinControls.UI.PropertyGridItemEditorInitializedEventArgs e)
{
    PropertyGridColorEditor colorEditor = e.Editor as PropertyGridColorEditor;
    if (colorEditor !=null)
    {
        RadColorBoxElement el = colorEditor.EditorElement as RadColorBoxElement;
        ((RadForm)el.ColorDialog.ColorDialogForm).Load += ColorDialogForm_Load1;
    }
}

private void ColorDialogForm_Load1(object sender, EventArgs e)
{
    RadColorDialogForm form = sender as RadColorDialogForm;
    RadPageView pageView = form.RadColorSelector.Controls["radPageView1"] as RadPageView;
    Telerik.WinControls.UI.RadColorPicker.ProfessionalColors professionalColors = 
        pageView.Pages[3].Controls["professionalColorsControl"] as Telerik.WinControls.UI.RadColorPicker.ProfessionalColors;
    foreach (Control c in professionalColors.Controls )
    {
        RadSpinEditor spinEditor = c as RadSpinEditor;
        if (spinEditor!=null)
        {
            spinEditor.SpinElement.TextBoxItem.Enabled = false;
        }
    }
}

To reproduce: Using the below code, type something in the text box and execute the button shortcut => the caret remains where it was

 protected override void OnLoad(EventArgs e)
        {
            base.OnLoad(e);

            AddTextBoxControl();

            radButton1.ButtonElement.Shortcuts.Add(new RadShortcut(Keys.Alt, new Keys[] { Keys.R }));
        }

        private void radButton1_Click(object sender, EventArgs e)
        {
            radTextBoxControl1.Text = "";
        }

Workaround:
Instead of setting the Text to empty string, use the control Clear method.

Steps to reproduce: 
public Form1()
{
    InitializeComponent();
    this.Text = Telerik.WinControls.VersionNumber.Number;
    this.radMaskedEditBox1.Culture = new System.Globalization.CultureInfo("nl-BE");
    this.radMaskedEditBox1.MaskType = Telerik.WinControls.UI.MaskType.Numeric;
    this.radMaskedEditBox1.Mask = "C";
    this.radMaskedEditBox1.Value = 570.00;
}

private void radButton2_Click(object sender, EventArgs e)
{      
    this.radMaskedEditBox1.Culture = new System.Globalization.CultureInfo("en-US"); 
}

private void radButton1_Click(object sender, EventArgs e)
{
    this.radMaskedEditBox1.Culture = new System.Globalization.CultureInfo("nl-BE");
}

Run the application and change the culture between Dutch and English, you will see that the value is reset instead keep it.

Workaround: 
CultureInfo providerDutch = new CultureInfo("nl-BE");
CultureInfo providerEnglish = new CultureInfo("en-US");

public Form1()
{
    InitializeComponent();
    this.Text = Telerik.WinControls.VersionNumber.Number;

    this.radMaskedEditBox1.Culture = providerDutch;
    this.radMaskedEditBox1.MaskType = Telerik.WinControls.UI.MaskType.Numeric;
    this.radMaskedEditBox1.Mask = "C";
    this.radMaskedEditBox1.Value = 570.00;
}

private void radButton1_Click(object sender, EventArgs e)
{
    double tempValue = double.Parse(this.radMaskedEditBox1.Value.ToString(), NumberStyles.Currency | NumberStyles.AllowThousands | NumberStyles.AllowDecimalPoint, providerEnglish); 
    this.radMaskedEditBox1.Culture = new System.Globalization.CultureInfo("nl-BE");
    this.radMaskedEditBox1.Value = tempValue;
}

private void radButton2_Click(object sender, EventArgs e)
{
    double tempValue = double.Parse(this.radMaskedEditBox1.Value.ToString(), NumberStyles.Currency | NumberStyles.AllowThousands | NumberStyles.AllowDecimalPoint, providerDutch); 
    this.radMaskedEditBox1.Culture = new System.Globalization.CultureInfo("en-US");
    this.radMaskedEditBox1.Value = tempValue;
}

To reproduce:

this.radDateTimePicker1.Format = DateTimePickerFormat.Short;
this.radDateTimePicker1.Value = new DateTime(2016, 5, 12);
this.radTextBox1.Text = "9/5/2016";

Second scenario:

this.radDateTimePicker1.Format = DateTimePickerFormat.Short;

If you copy "1/7/16" and paste it into RadDateTimeicker, the result date will be "1/7/1616". In the previous version, the result was correct 1/7/2016.

Copy the value in the text box and paste it in RadDateTimePicker.

Workaround: 

public Form1()
{
    InitializeComponent();
    this.radDateTimePicker1.Format = DateTimePickerFormat.Short;
    this.radDateTimePicker1.Value = new DateTime(2016, 5, 12);
    this.radTextBox1.Text = "9/5/2016";
    this.radDateTimePicker1.ValueChanging += radDateTimePicker1_ValueChanging;

    this.radDateTimePicker1.DateTimePickerElement.TextBoxElement.TextBoxItem.TextBoxControl.KeyPress += TextBoxControl_KeyPress; 
}

string clipboardData;

private void TextBoxControl_KeyPress(object sender, KeyPressEventArgs e)
{
    if (e.KeyChar == '\x16')
    {
        if (clipboardData != null)
        {
            this.radDateTimePicker1.Text = clipboardData;
            clipboardData = null;
        }
    }
}

private void radDateTimePicker1_ValueChanging(object sender, Telerik.WinControls.UI.ValueChangingEventArgs e)
{
    if (clipboardData == null)
    {
        clipboardData = RadMaskedEditBoxElement.GetClipboardText();
    }
}

How to reproduce: 
public Form1()
{
    InitializeComponent();

    this.radMaskedEditBox1.Culture = new CultureInfo("ar-EG");
    this.radMaskedEditBox1.Mask = "c";
    this.radMaskedEditBox1.MaskType = Telerik.WinControls.UI.MaskType.Numeric;
}

Workaround: handle the KeyDown event
 private void radMaskedEditBox1_KeyDown(object sender, KeyEventArgs e)
 {
     if (this.radMaskedEditBox1.SelectionLength == this.radMaskedEditBox1.Text.Length)
     {
         this.radMaskedEditBox1.SelectionLength = 0;
     }
 }

To reproduce:
- Set the mask to regex and paste with Ctrl + V.

Workaround:
private void RadmaskedEditBox1_KeyPress(object sender, KeyPressEventArgs e)
{
    if (e.KeyChar == '\x16')
    {
        radmaskedEditBox1.MaskedEditBoxElement.TextBoxItem.Paste();
    }
}

To reproduce:
Thread.CurrentThread.CurrentCulture = new System.Globalization.CultureInfo("es-CO");
radMaskedEditBox1.MaskType = Telerik.WinControls.UI.MaskType.Numeric;
radMaskedEditBox1.Mask = "C2";
radMaskedEditBox1.Culture = new System.Globalization.CultureInfo("es-CO");

Click in the masked edit box and press the decimal separator key in the num pad, the cursor is not moved to the desired position.

Workaoround:
 private void RadMaskedEditBox1_KeyUp(object sender, KeyEventArgs e)
{
    if (e.KeyValue ==  46)
    {
        var textBoxItem = this.radMaskedEditBox1.MaskedEditBoxElement.TextBoxItem;

        int indexOfDecimalSeparator = this.radMaskedEditBox1.MaskedEditBoxElement.TextBoxItem.Text.ToLower().IndexOf(',');
        if (indexOfDecimalSeparator + 1 <= textBoxItem.Text.Length)
        {
            textBoxItem.SelectionStart = indexOfDecimalSeparator + 1;
        }
        else
        {
            textBoxItem.SelectionStart = indexOfDecimalSeparator;
        }
        e.Handled = true;
    }

}

To reproduce: 

this.radDateTimePicker1.Format = DateTimePickerFormat.Custom;
 this.radDateTimePicker1.CustomFormat = "MM/yyyy";
this.radDateTimePicker1.Value = new DateTime(2016, 01, 31);

Select the month part and try to change it to 02.

Workaround: initialize with the first day of the month.