The buyer came from a professional malicious feedback organization.
He will deliberately saying you send wrong item or damaged item or other problem
If you want proofs such as photos，he will not provide，and left bad feedback and open case on you.
If in the end,Amazon or ebay not stand on your side, and force you to refund money,he wins,he basically get the item for free,and he can resell the item without any cost. That is how he make profits.

Please Note that, for this kind of issue,as seller,you have absolute right to ask for proofs. No one can accuse you for doing something wrong without provide evidences. We don't think you can put anyone you hate into jail by just saying he murdered someone without provide evidences.

Please insist to ask for evidences, and block this buyer for future purchase.

The platform thinks you have to refund in the end is something better than show the weakness to malicious buyers. Even if Amazon or eBay favor buying, in this case, you still have the possibility of winning the case.