Cassette gets stuck at some specific locations, causing chain to jump when I stop pedaling sometimes

Every now and then the chain jumps violently when I stop pedaling, not quite enough to derail but close. I noticed when backpedaling slowly like in the video, the chain gets stuck at some specific locations on the cycle, causing the wheel to spin (towards end of video). It only does it at low speed but I think it shows the issue I have.

I tried spinning the jockey disks without the chain and they both spin with little resistance (as far as I can tell, I don’t know what normal resistance is). I tried spinning the cassette without the chain and there are indeed some positions where it will spin the wheel with it until enough resistance is put on it.

I should also mention the derailleur cage touches the chain a little in certain gears, it doesn’t seem to be the cause of this friction but could contribute? Or could be normal? — not sure

Doesn’t seem to be the cassette sticking. Could be damaged links in the chain. I’d start with replacing the chain and see if that fixes it. I don’t think it’s bad jockey wheels or rear mech. Is there a front mech as well or is this a 1x drive?

ETA: what does it do when you’re actually pedaling it to spin the wheel? Same thing?

First check that there aren’t any sticky links in the chain, but if you feel random resistance when just spinning the cassette by hand your freehub bearings probably need replacement.

You have a stuck chain link. Did you recently try to replace a link with the original post? Take it out and replace it with a quick link and that should solve this problem.