Hello, First try to update the Firefox app on your Mac, then, later restart you Macbook, it should solve the bug you are having! Best!

Unfortunately Firefox is up to date so that will not help

Could you try disabling Firefox from using hardware acceleration? This is a potential workaround for incompatibilities between Firefox and your graphics card/chipset driver software. This article describes where to make that change: Firefox's performance settings. This will take effect the next time you exit Firefox and start it up again. Any difference?

Since hardware acceleration improves the appearance of fonts and animations, you may want to check whether graphics card/chipset driver updates are available for your system. This article suggests safe ways to do that: Upgrade your graphics drivers to use hardware acceleration and WebGL.

Tried that as well, it is disabled all ready, this is proving to be quite a challenge