As the title says I've noticed that in the past day kBin often freezes up when I view a thread (Firefox pops up asking me if I want to stop the tab or not). I use Firefox on EndeavourOS but I didn't have any problems with it for the past 2 weeks.
I feel like there's the slight possibility you can't reply to this thread, because of aforementioned issue. If true, perhaps posting an issue in the repo or joining the matrix might work better for you
Itemize what extensions you are running and try creating a vanilla prefix (firefox -P), then testing it there, and use process of elimination to narrow down which one(s) may be the root cause.
Well, if you aren't running browser extensions (add-ons) in your browser, then that can't be the cause. Sometimes extensions may conflict with the browser and drag performance, so it can be good to get closer to a vanilla state, but sounds like you already are there.