Sometimes windows will just look like this? Minimizing or changing tabs usually fixes it, sometimes resizing. If I select a folder or a menu option it usually looks normal while highlighted. Happens most often with folders and with the software manager. Also happens to the text in Nicotine+ sometimes and the text editor. Never seems to happen to Firefox or VLC. I don’t even know what to call what is happening visually here so I haven’t been able to find anything just by googling.
i think i’ve managed to get to this state exactly once, but i don’t remember how i got there and what machine it was. i just know that it was a machine i tried multiple distros on and so i can confidently say that, in my case, it was not a hardware, but a software issue. i hope that nothing of value is broken for you either. good luck!