@TheMagicM
I say just ignore them. You said AS-IS, and didn't guarantee no DOA, so you're in the clear. Maybe, if you want to do something at all, offer to be a witness (or whatever) that it was working when they make a claim for the shipping insurance. Just hope the post office doesn't know that those old cameras apparently are on the verge of death anyway. I tried to get the VCR part of my old Panasonic camera fixed, and the repair guy refused because once he'd fix one thing, another thing would break and people always came back complaining that he didn't fix it. He also was amazed because mine was the only one he'd ever seen that had a working camera part. Anyhoo, I say steal some slang from the movie Hot Fuzz and tell that guy to "jog on". :-)
If he threatens negative feedback, you can report him to ebay since that's feedback extortion.