Use attached to reproduce.

1 - In the First Text Box (the Masked Box) type 1
2 -  Click the "GO" button. The text box shows 1 and the VALUE is displayed from the Edit box correctly as 1
3 - Select the 1 in the edit box and CTRL + DELETE to clear the field
4 - Click the "GO" button. The text box shows NULL and the VALUE is displayed from the Edit box correctly as NULL
5 - Highlight the text in the "Paste Me!" text box and Copy the text to Clipboard.
6 - Paste the clipboard into the Masked t Edit box
7 - Click "GO". The mask text box correctly displayed NULL however the returned VALUE is 1

 

To reproduce:

Add the following code:
int count = 0;
private void dateTimePicker1_ValueChanging(object sender, Telerik.WinControls.UI.ValueChangingEventArgs e)
{
   
    if (count == 2)
    {
        e.Cancel = true;
    }
    count++;
}

- Select the year and press down multiple times. After some time the event is not fired any more. 

Workaround:
class MyMaskDateTimeRpovider : MaskDateTimeProvider
{
    public MyMaskDateTimeRpovider(string mask, CultureInfo culture, RadMaskedEditBoxElement owner) : base(mask, culture, owner)
    { }
    public override object Value
    {
        get { return base.Value; }
        set
        {
            typeof(MaskDateTimeProvider).GetField("oldValue", BindingFlags.Instance | BindingFlags.NonPublic).SetValue(this, null);
            base.Value = value;
        }
    }

}

To reproduce:
- Use the Fluent theme with RadSpinEditor on a HDPI monitor.

Workaround:
 var borderPrimitive = radSpinEditor1.SpinElement.Children[1] as BorderPrimitive;
borderPrimitive.BottomWidth = 2;

To reproduce: 

            this.radBrowseEditor1.Value = @"D:\Projects";
            this.radBrowseEditor1.ReadOnly = false; 
            this.radBrowseEditor1.BrowseElement.ShowClearButton = true;

You will notice that the clear button is not shown.

Workaround:

            LightVisualButtonElement btn = new LightVisualButtonElement();
            btn.Text = "X";
            btn.Click += btn_Click;
            btn.StretchHorizontally = false;
             
            this.radBrowseEditor1.BrowseElement.BrowseButton.Parent.Children.Add(btn);


        private void btn_Click(object sender, EventArgs e)
        {
            this.radBrowseEditor1.Value = null;
        }

See attached video to reproduce.

To reproduce:
- Set the DropDownSizingMode to None
- Show the popup several times.
- Each time the height is increased.

Workaround:
var popup = radPopupEditor1.PopupEditorElement.PopupForm as RadPopupContainerForm;
popup.SizingGrip.MinSize = new Size(0, 0);

How to reproduce:  The spell checker`s AutoSpellCheckControl property must not be set. Add a ContextMenuStrip with several items and use it with a standard text box. Then perform a spell check with the RadSpellChecker control, e.g. like this: 

Me.RadSpellChecker1.Check(Me.TextBox1)

Then right-click in the text box, the context menu will not be shown.

Workaround: use RadContextMenu
https://docs.telerik.com/devtools/winforms/menus/contextmenu/context-menus

Use the following code:
public RadForm1()
{
    InitializeComponent();
    radMaskedEditBox1.MaskType = Telerik.WinControls.UI.MaskType.Numeric;
    radMaskedEditBox1.Mask = "d0";
    radMaskedEditBox1.EnableNullValueInput = true;

    radMaskedEditBox1.TextChanged += RadMaskedEditBox1_TextChanged;
    radMaskedEditBox1.ValueChanged += RadMaskedEditBox1_ValueChanged;

    radMaskedEditBox1.Value = null;

}

private void RadMaskedEditBox1_ValueChanged(object sender, EventArgs e)
{
    Console.WriteLine(radMaskedEditBox1.Value);
}

- Type "1", you will notice that the value is still null.
- Type "2", the value is now correct.

Workaround:
private void RadMaskedEditBox1_ValueChanged(object sender, EventArgs e)
{
    if (radMaskedEditBox1.Text != "" )
    {
        var provider = radMaskedEditBox1.MaskedEditBoxElement.Provider;
        Console.WriteLine(provider.Value);
    }
    else
    {
        Console.WriteLine(radMaskedEditBox1.Value);
    }
  
}
er.Value);

To reproduce:       
 Me.RadDateTimePicker2.Format = DateTimePickerFormat.Custom
 Me.RadDateTimePicker2.CustomFormat = "hh:mm tt"

Select the hours part with the mouse, the selection is affected correctly. Select the minutes part, the selection is affected correctly. Select the AM/PM part, the selection is again affected correctly. Now, try to select again the minutes part. You will notice that the cursor is affected correctly but the selection is missing. Once you select the AM/PM part then the selection is not updated properly with the mouse anymore.

Workaround:

Me.RadDateTimePicker1.DateTimePickerElement.TextBoxElement.Provider = New CustomMaskDateTimeProvider(Me.RadDateTimePicker2.DateTimePickerElement.TextBoxElement.Mask, Me.RadDateTimePicker2.Culture, Me.RadDateTimePicker2.DateTimePickerElement.TextBoxElement)


    Public Class CustomMaskDateTimeProvider
        Inherits MaskDateTimeProvider

        Public Sub New(mask As String, culture As CultureInfo, owner As RadMaskedEditBoxElement)
            MyBase.New(mask, culture, owner)

        End Sub
        Public Overrides Function SelectCurrentItemFromCurrentCaret() As Boolean
            Dim currentSelection As Integer = Me.TextBoxItem.SelectionStart
            Dim currentPos As Integer = 0
            Dim selected As Boolean = False

            'If Me.List(Me.SelectedItemIndex).type = PartTypes.AmPm Then
            '    Return True
            'End If

            For i As Integer = 0 To Me.List.Count - 1
                Dim part As MaskPart = Me.List(i)

                If SelectMilliseconds(i, part) Then
                    Exit For
                End If

                If currentSelection >= part.offset AndAlso currentSelection <= part.offset + part.len AndAlso Not part.[readOnly] AndAlso part.type <> PartTypes.Character Then
                    Me.TextBoxItem.SelectionStart = Me.List(i).offset
                    Me.TextBoxItem.SelectionLength = Me.List(i).len
                    Me.SelectedItemIndex = i
                    selected = True
                    Exit For
                End If

                currentPos += part.len
            Next

            Return selected
        End Function

        Private Function SelectMilliseconds(ByVal i As Integer, ByVal part As MaskPart) As Boolean
            If part.type = PartTypes.MiliSeconds AndAlso Me.value.Millisecond Mod 10 = 0 AndAlso part.trimsZeros Then
                Dim newLen As Integer = part.len

                For power As Integer = 1 To part.len

                    If Me.value.Millisecond Mod Math.Pow(10, power) = 0 Then
                        newLen -= 1
                    Else
                        Exit For
                    End If
                Next

                Me.textBoxItem.SelectionStart = Me.list(i).offset
                Me.textBoxItem.SelectionLength = newLen
                Me.SelectedItemIndex = i
                Return True
            End If

            Return False
        End Function
    End Class

https://msdn.microsoft.com/en-us/library/system.windows.forms.maskedtextbox.maskcompleted(v=vs.110).aspx

To reproduce:
- Open the attached project.
- Click the day part and press N
- Click the hour part and press N - PM is changed to AM

Workaround:
public RadForm1()
{
    InitializeComponent();
    radDateTimePicker1.Format = DateTimePickerFormat.Custom;
    radDateTimePicker1.CustomFormat = @"yyyy/MM/dd hh:mm:ss tt";
    radDateTimePicker1.DateTimePickerElement.TextBoxElement.TextBoxItem.KeyPress += TextBoxItem_KeyPress;
}
 
private void TextBoxItem_KeyPress(object sender, KeyPressEventArgs e)
{
    if (e.KeyChar == 'n')
    {
        e.Handled = true;
        radDateTimePicker1.Value = DateTime.Now;
    }
}

We should also add padding to the RadTimePicker

Workaround: 
this.radSpinEditor1.SpinElement.Padding = new Padding(2, 0, 0, 0);
this.radTimePicker1.TimePickerElement.Padding = new Padding(2, 0, 0, 0);

To reproduce:
- Open the demo application.
- Open the PropertyGrid -> FirstLook example.
- Open the color dialog editor multiple times. 

 

Use attached to reproduce.
- Open the dialog multiple times.

To reproduce: set  this.radMaskedEditBox1.MaskType = Telerik.WinControls.UI.MaskType.IP; and try to enter '300' for the first part of the IP address. A message pops up  explaining that the value is outside the valid range. This message can't be changed. It should allow localizing. In addition, a RadMessageBox should be shown as well.

Use attached to reproduce.

Workaround: 
Use RadTextBox.

To reproduce:

        Me.RadDateTimePicker1.Format = DateTimePickerFormat.Custom
        Me.RadDateTimePicker1.CustomFormat = "MM/dd/yyyy"

        Dim provider As MaskDateTimeProvider = TryCast(Me.RadDateTimePicker1.DateTimePickerElement.TextBoxElement.Provider, MaskDateTimeProvider)
        provider.AutoSelectNextPart = True

 If you type in 01/01/50, RadDateTimePicker displays 01/01/1950 which is correct. If you type in 01/01/2050, the system is again changing the century and display 01/01/1950 which is incorrect. 

Workaround: use a custom mask provider to customize how the autocompletion work:
    Public Class CustomMaskDateTimeProvider
        Inherits Telerik.WinControls.UI.MaskDateTimeProvider
        Public Sub New(mask As String, culture As CultureInfo, owner As RadMaskedEditBoxElement)
            MyBase.New(mask, culture, owner)

        End Sub

        Protected Overrides Function HandleKeyPress(part As MaskPart, e As KeyPressEventArgs) As Boolean
            Dim value As Integer = 0
            If Not Integer.TryParse(e.KeyChar.ToString(), value) Then
                Return True
            End If

            Dim stringValue As String = String.Empty
            If part.type = PartTypes.MiliSeconds Then
                Dim newValue As Integer = CInt((part.value / Math.Pow(10, (3 - part.len)))) * 10 + value
                part.value = newValue Mod CInt(Math.Pow(10, part.len))
            Else
                stringValue = part.value.ToString()
                If stringValue.Length = part.len AndAlso stringValue.Length >= part.maskPart.Length Then
                    stringValue = stringValue.Substring(1)
                End If

                If Me.AutoCompleteYear AndAlso stringValue.Length = 1 Then
                    stringValue = String.Empty
                End If

                part.value = Integer.Parse(stringValue & e.KeyChar)
            End If

            If part.type = PartTypes.Year AndAlso part.maskPart.Length = 2 Then
                Dim len As Integer = part.value.ToString().Length
                part.value = Integer.Parse(String.Format("{0}{1}", DateTime.Now.Year.ToString().Substring(0, 2), part.value.ToString().Substring(len - 2, 2)))
            End If

            If Me.AutoCompleteYear AndAlso part.type = PartTypes.Year Then
                Dim len As Integer = part.value.ToString().Length
                If len >= 2 Then
                    part.value = Integer.Parse(part.value.ToString().Substring(len - 2, 2))
                End If

                'If part.value >= 50 AndAlso part.value <= 99 Then
                '    part.value += 1900
                'ElseIf part.value >= 500 AndAlso part.value <= 999 Then
                '    part.value += 1000
                'ElseIf part.value < 50 OrElse (part.value > 99 AndAlso part.value < 500) Then
                part.value += 2000
                ' End If
            End If

            If part.value > part.max OrElse part.value < part.min Then
                part.value = value
            End If

            Return True
        End Function
         
    End Class

  Me.RadDateTimePicker1.Format = DateTimePickerFormat.Custom
        Me.RadDateTimePicker1.CustomFormat = "MM/dd/yyyy"

        Me.RadDateTimePicker1.DateTimePickerElement.TextBoxElement.Provider = New CustomMaskDateTimeProvider(Me.RadDateTimePicker1.DateTimePickerElement.TextBoxElement.Mask, Me.RadDateTimePicker1.Culture, Me.RadDateTimePicker1.DateTimePickerElement.TextBoxElement)

        Dim provider As MaskDateTimeProvider = TryCast(Me.RadDateTimePicker1.DateTimePickerElement.TextBoxElement.Provider, MaskDateTimeProvider)
        provider.MaxDate = Me.RadDateTimePicker1.DateTimePickerElement.MaxDate
        provider.AutoSelectNextPart = True
        provider.AutoCompleteYear = True

Thus, the year always be 2000+.

Use attached to reproduce:
- Disable and then enable the RadSateTimePicker
- You will notice that even the checkbox is unchecked the control is enabled. 

Workaround:

radDateTimePicker1.Enabled =true;
if (!radDateTimePicker1.DateTimePickerElement.Checked)
{
    radDateTimePicker1.DateTimePickerElement.TextBoxElement.TextBoxItem.HostedControl.Enabled = false;
}

To reproduce:
this.radDateTimePicker1.DateTimePickerElement.TextBoxElement.MaskType = MaskType.FreeFormDateTime;

And try pasting a date, or some free text.

 

To reproduce:

            this.radTextBox1.NullText = "text";
            this.radTextBox1.TextBoxElement.TextBoxItem.NullTextColor = Color.Red;

Workaround:  this.radTextBox1.TextBoxElement.NullTextColor = Color.Red;