I have had this issue for a couple weeks now with youtube. When running in a private tab it will frequently not accept input for something like 10 seconds at a time. Playback works totally fine, no real stuttering or lag in the video, but pressing pause will generally take significant time to actually pause. This is true of all other inputs including keyboard commands, clicking on links, right click, etc. It seems to have a rolling window where inputs are accepted because if I wait for clicking play to work I can also quickly change the volume or right click a link. It'll even accept the input if I'm in a different window (like if I hit play then click over to my second monitor). This doesn't seem to happen in a normal window, only private. All other firefox tabs work totally fine with none of this lag, nor do I see any other issues on my computer. I haven't noticed any spikes in hardware usage nor am I using anywhere near all of my PC's resources. I'm only running 2 extensions I think would interfere here (ublock origin and enhancer for youtube) and I've tried running with them disabled to no effect. All my extensions are up to date, as are my browser and OS, this has persisted through restarts (though it seems to take some time to come into effect after a restart). I've tried disabling hardware acceleration and clearing the cache. So yeah, no idea what's wrong. It's not like unusable, just really annoying. Thanks to anyone that helps.