I sold a DVD player on eBay a short while back and the buyer opened a dispute saying it did not work. Paypal put the money in my account on hold whilst it was sorted. The DVD player worked fine when I sent it via recorded delivery and looking through the buyers feedback he had purchased the same player only a month before off another seller.
The buyer then sent me an email saying he had purchased the other but it had broke and thats why he was buying mine, also could I refund him before I received the player back as he needed to buy another.
Paypal were no help and just kept the money whilst I sorted it. Someone gave me the advice to ask him to return the player so I could check the secret mark I put inside the player along with the serial number.
Surprise surprise it started working....
Paypal would have given him his money back regardless of whether he did send me a different player back as I could never prove it was a diffent player to Paypal regardless of serial numbers or secret marks. I would of had to contact the Police and report it which would have led no where.