White box appears on fullscreen when a key is pressed

[Paopee]

Appears on Youtube when fullscreen and keyboard is pressed.

https://drive.google.com/file/d/10Z-TZMzX2oqLQgFUyAVQwExn8jvZTZzD/view?usp=sharing

I think it's not app related as it also appears on AnyDesk.

https://drive.google.com/file/d/10a-_PUD3KovSMIaaaXbpoA7MIo5odaYu/view?usp=sharing

It appears when it's full screen and if you press Space or Tab on the keyboard. I'm currently using Samsung S7+ Tablet.

Any fix for this? 

[Shazzkid]

Hmmm, try checking some of your Accessibility settings.