I played a bit more with the "crashing"-the-camera with a piece of paper bug and confirmed that the bug is indeed in camera. To be precise, I've sniffed the USB packets and written a dumper that dumped individual MJPEG frames (which are just JPEG files).

As soon as the frames reached around 850KB (that sounds awfully close to 0xd0000 bytes) some - but not all - JPEGs were slightly corrupted. There were 3-13 corruptions reported by libjpeg's decoder per file (and I'm guessing some undetected ones as well). I'm a bit puzzled about the nature of these corruptions, since they are in the middle of a frame.

Anyway, USB dumps are from Windows, so it's not a Linux-only issue.

And as far as OBS goes, it's probably just a case of OBS overreacting to some error report from ffmpeg/jpeg decoder.

I think I'm going to leave it as this, since I realllyyyy don't want to dig into C920's firmware. Will write this down on my blog though I guess.