King Snake skin problem help

[TRD]

To me that looks like a snake that is in a form of pain or irritantion, be it internal or external. Neurological damage also shows itself as abnormal behavior, but what your snake is doing looks deliberate. Have you tried to remove him from his enclosure and into a plastic tub on newspaper for a while? Just at room temperature (about 77 F). Maybe the bedding just irritates him, or something in the air, can be as simple as that really.

See if the situation improves.

Can also be he has some internal issues, which the vet usually will not spot (they usually check external parasites and general health of the reptile). You know, if you are in pain you touch the spot where it hurts, rub it or whatever. You see what your snake is doing? Rubbing its body together and biting itself. They don't have an option when they are in pain, this is what they can do without arms...

I'm not going to question your vet's competency or anything, but it may be advisable to get in contact with a specialized reptile/snake vet, even if just telephone consultancy. He may be able to help also when showing the video to him over e-mail, also providing the information already shared to you by your regular vet. IF there's anything you can do to help him, it should be done.