I have also asked same question earlier (thinking it was screen tearing) but did not got solution.
Screenshots of issues:
My specs:
All system up to date with latest ubuntu 20.04. No additional hardware (Graphic card and all).
1 Answer
The same issue occurred in Lubuntu but with more occurrences (Link). I think there was some issue with the core OS or drivers. After installing the newer version of Ubuntu 20.04.2 the issue is gone.
