ugh, I’m out of idea tbh. Seems you need to ask others about it. Also are your video in 2k or probably 4k? or it’s normal 1080 or even only 720?

Is the about:cache is full? Or it’s too small? I mean if it’s to small it could be the cause.

By anychance, do you have free ram? Sometimes this happen when the ram is not available… so yeah… You should check it first. Also check about:memory I guess