22-02-2020 7:21 AM
You have been terribly unlucky! Whilst online selling is obviouly open to abuse, of course there is no one to physically check items being sent or received, I know you say photos can prove no damage , but if it were a court of law , it couldn't stand up as evidence, as there is no proof that is the same item!
So, you do not have to comply to any partial refunds, I would suggest apologising ( albeit through gritted teeth) and then say to follow eBay rules they need to send the item back for a full refund. I'm sure you'll find many will not do that.
If they do open a case, no point fighting it, it is all automated. So refund when the item is back ,or tracking showing it's been posted. Then if ulterior damage has been done, you call eBay CS from the Help & Contact tab above, fight your case and explain that the buyer is abusing their 30 day MBG, buyer may have a record of doing this.