This is a hard one to describe and also reproduce. Once in a while, probably a few times a day, I will have a tab open on a website that stops responding to input, as in, I can't type anything in forms, I can't scroll up or down on the site, etc.
HOWEVER, if I switch to another tab and back again, whatever actions I took did actually happen. I just can see them happen as I do them.
Tried to record an example of this happening just. It doesn't seem to be associated with any specific site.
responsive tabs
Version 0.99.126.4.1.8-rc
Sonoma (14)