V18.3.0.38 on Android
So here is a strange thing.
Setup a masked edit like this:
<syncmaskededit:SfMaskedEdit Value="{Binding Filename}" MaskType="RegEx" Mask="\w{30}" ValidationMode="KeyPress" >
</syncmaskededit:SfMaskedEdit>
So we should accept 30 alphanumeric characters.
Start typing 'a', 'b', 'c', space
Now the screen shows correctly "abc" and the space is rejected
Continue typing 'd','e','f'
The input stops accepting characters!, it now shows "abcd" - the e and f are ignored and not entered
Now use the backspace key to delete,
tap it once and display shows "abcd",
tap it again and display shows "abcdd", - where does this extra 'd' come from???
tap it third time, display still shows "abcdd" - still the extra 'd' is show!!!
tap it fourth time and display shows "abcd" and now you can again enter more characters and they get entered into the string.
The binding value, Filename reflects what is shown on the display.