Firefox freezes sometime on attempt to move using mouse

Ubuntu 20.04.6 LTS, IceWM. Latest FF downloaded from mozilla website. System does not receive any mouse click (Left, R.). I can't switch to another application (using mouse or keyboard). I had to close FF using Alt-F4 key. System works usualy since then. Any idea please ?

Code:maketopsite@ub:~$ apulse /media/maketopsite/tmp/ff/firefox/firefox --profile ~/delete
[GFX1-]: GFX: RenderThread detected a device reset in PostUpdate
maketopsite@ub:~$Edit: Optimus laptop, latest NVIDIA proprietary drivers installed, Xorg.