Please explain the problem in detail. What happens? What is/are the exact error message(s) ?

It's hard to describe in words. It's better to watch videos. Various parts of the screen are twitching, and the image is falling apart.

You can try to disable hardware acceleration in Firefox.

• Options/Preferences -> General: Performance
  remove checkmark: [ ] "Use recommended performance settings"
  remove checkmark: [ ] "Use hardware acceleration when available"
• https://support.mozilla.org/en-US/kb/performance-settings

Close and restart Firefox after modifying the setting for changes to take effect.

• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

You can check if there is an update for your graphics display driver and check for hardware acceleration related issues.

• https://support.mozilla.org/en-US/kb/upgrade-graphics-drivers-use-hardware-acceleration

cor-el, Thank you very much! Disabling hardware acceleration helped!