The Value property of the TextInput is not correctly updated when using the On-Screen Touch keyboard when using no mask (Mask=""). We managed to reproduce the issue on Windows 8.1, 10. The behavior is different in both Windows OS. To get the Touch Keyboard you can check the following link.

Windows OS  8.1 - When you enter text and pressed backspace key- the value property is not updated the first time.

Windows OS 10 - When you enter text and pressed backspace key the value property is updated correctly. But if you HOLD THE BACKSPACE KEY the Value property ignored this behavior.