My sister in law once lost out to a dodgy buyer. She sold a brand new unwanted present, the guy complained that it was old and worn, then sent back an empty box.
I have heard about people switching items, there’s has broken or stopped working, so they buy a replacement from eBay, then complain that what they’ve bought was faulty. They then return their old unit and get their money returned through eBay, so they get a free replacement.