I don't know why you are downvoted. My best bet is that the equipment is some crappy cheap stuff and somehow the encoding process skips at some times for whatever reason. Maybe it's too hot, something overheats, buffers... or just a bug of some ancient software.

I suppose this is just a bad choice in equipment. For example, in Germany CCTV cams in underground stations seem to have an incredibly bad black/white low-resolution quality and when bad things happen people are supposed to recognize some blurry face..