firefox scrolling pauses

i've only seen this happen on firefox. the severity of it seems to vary among different websites. if i roll the mouse roller continuously, it keeps working. if i pause for a very short time, it still works. if i pause for over a second, rolling it again does nothing. if i wait 3-4 seconds or so, then roll it, it works, again.

any ideas what's going on? any ideas how to fix it?

i have firefox version 78.