I don't think it's a broken spring because it's not acting like a typical broken spring. This video was taken at least two minutes after the compressor had shut down and it had been banging for at least a minute before I could turn on the camera. Every broken spring I've seen, it will bang for maybe a second after the compressor shuts down.
The owner is aware that it is probably a sealed system issue and may not get his fridge back. I have a couple of things I'm going to try. I'll let you know what I find.