MaskedNumericInput with Mask = #6.3. When there is no digit grouping (you can turn it off from  the region / format settings in windows, no digit grouping means no symbol for grouping) the control produces Exception on load.

If you try to paste text in the RadMaskedTextInput control using the default ContextMenu, after the Clear button is pressed (or after delete with backspace), the Paste command is not working as expected.

Available in LIB version: 2014.3.1124

RadMaskedTextInput with no-mask => Mask="".

Selecting part of the value then paste works incorrectly. The selected text is not replaced and it is preserved, the copied text is inserted.

It is expected that the selected text is entirely replaced with the copied text.

GridView with GridViewDataColumn.CellEditTemplate.

In it MaskedTextInput is initially Collapsed. Double clicking the Cell will produce a Null refecence exception.

Users sometimes need to invoke Undo / Redo. Public command properties would be a possible way to go.

When using German Culture, NoMask and FormatString = "n0" , an incorrect input is produced.

For example pressing 4 times "6" will produce a Value of 7.

This is a parsing issue (6666 becomes 6.666 where "." is a grouping symbol in German Culture).

Then 6.666 is parsed with rounding to 7.

In MaskedTextInput the ClearButton will make the Value "" but it should make it NULL. All other InputControls have null value after pressing ClearButton.

No-masked TextInput works fine - the ClearButton makes the Value Null.

As a workaround, you can use the ClearCommand, bind it to Command from your ViewModel and the execute handler can set the bound Value to null.

Pressing ClearButton of the RadMaskedDateTimeInput will place the caret on the last position.

It must place the caret on the first position. 

When using implicit styles mechanism and you merge Telerik.Windows.Controls.Input an exception is thrown.

If the XAML file is set with BUILD ACTION PAGE the issue is not reproducible.

Another workaround is to reference dlls only, not xaml theme files.

Issue is reported in several msdn / stackoverflow threads and it appears to be an MS-TextBox one. 
http://stackoverflow.com/questions/6850713/weird-xaml-parsing-error-when-trying-to-set-textbox-isreadonly 

MaskedInput focus behaves different when it is set in code behind. When the textbox is on focus and new character is entered the text remains the same and the new character is added at the beginning of the textbox.

Scheduled for:
The fix for this issue will be available with LIB (version 2019.1.128) scheduled for publishing on Monday, 28th January 2019.

If you set the OS culture to Dutch (Belgium) and set the Decimal symbol to "." and the Digit grouping symbol to "," you are not allowed to enter 5 digits into the RadMaskedNumericInput control.

When the Value of the RadMaskedInput (all RadMaskedInput controls) is changed in code behind, the ValueChanged event isn't fired.

We have MaskedTextInput with InputBehavior set to Replace.

When we select part of the value or the whole value and then insert a symbol, only the first selected symbol is replaced but not the whole selected text.

When UpdateValueEvent is set on PropertyChanged and the mask uses upper/lower token(s) the letters/characters are updated to uppercase after filling the mask. The control should update its text on every key stroke.

Update:
We are closing this issue because this is expected behavior in MaskedInput.
Value property is updated if all required symbols (required from the Mask) are populated. If you need the Value to be updated on every symbol entered you can set the property AllowInvalidValues = True.

Currently, performing consecutively paste operation does not work like in TextBox. In TextBox the strings are concatenated but in MaskedTextInput the caret is in the beggining and only the first paste is successful. 

If Mask = "\A\B\C\D####" (A, B, C, D are escaped) and NumericInput is used. Select All , then typing 1234 produces something like 4312.

Available in LIB version: 2014.3.1222

Use No-Masked TextInput (Mask=""). Pressing delete will always place the caret on position 0.

Currently this property works only in MaskedTextInput.

In Q3 2013, Focus() or KeyBoard.Focus() cannot focus the MaskedInputControls so that their Caret is blinking and ready to receive input.
Also, FocusManager.FocusedElement used to do the same  in previous releases but in Q3 it doesn't.

Pasting 5788250000028292 in NumericInput with Mask = # 19 will cut the last digit 2.
Pasting the same number in CurrencyInput will produce an exception.