Im afraid you won't win, I had a very similar case, whereby a Buyer purchased an item from me, had it a couple of weeks then decided she didnt want it, so immediately left horrible negative feedback, then got onto Paypal asking for an immediate refund, because the item was in such a state etc etc: - no matter how many emails I wrote to Ebay, calls to Paypal, (who assured me they would look into it thoroughly) - Paypal granted her a full refund, stipulating that she mail the garment back to me, which she did, but when I received it, it REALLY was in bad condition,,- kind like she had dragged it around the yard - I immediately phoned Paypal - end of story, the Buyer won, I lost, and now have item back, very much the worse for wear.

So, back to your problem, I suggest you just accept it, seems whether you are right or wrong, you will lose in the long run 😞