dh sold a car part on ebay (catalytic convertor). It came off his car and was in working order, he was there when it was removed and kept it to sell on.
Buyer has come back to say it isn't fit for purpose as the internal (expensive bits!) parts have been removed and want a refund and dh to pay for postage back. There is no explanation other than the buyer removing them for his own use.
They have opened a dispute in ebay. What happens/do we do now as we have no proof the internal bits were there?