I sold an electronic drum kit to a co-worker acquaintance 2 years ago. I delivered it to the guy's house, and sensed buyer's remorse the second I got there. He was telling me about another kit at a similar price. He said, "No worries," and made the exchange anyhow.
15 minutes later he calls and tells me they don't work. At all.
They worked fine when I checked them before packing them up.
When I got to his house they didn't work. I gave him his money back. To this day I feel near certain he messed with them, but I didn't have it in me to fight or argue.
I haven't sold a thing since, and refuse to - unless someone comes to my house, checks it out, and gives me cash knowing its a final sale.
Period.
I don't trust anyone anymore, and we're pretty defenseless when it comes to this kind of thing.
I only read the first post. I hope you came to some sort of fair resolution.