No Background effects (Teams web client)

for the last few months, I've been noticing a slightly annoying issue, where some meetings let me have a background effect, and others won't. even for recurring meetings, one day it'll work, the next it won't. it even varies as the day goes by, some meetings I can have background effects on my webcam, others I don't. It's been touch and go, and seemingly completely random. Has anyone else noticed similar? or knows what the issue is?