I sold my daughter's drum kit earlier on in the week. Expensive electronic kit. I know nothing about drum kits as I don't play. Someone bought it, he came round here it was set up - he had a quick play. I told him ot was all working as I believed it was. He's now emailed me to say the hihat pedal is faulty. I've no idea if he actually tested that when he was here or not as I don't even know what the hihat pedal is.
Now normally I'd say well sorry but its yours now. For all I know it became faulty when he transported it to his house. He had the opportunity to play/test it as much as he wanted and if he didn't test that bit when he was here its not my fault. However I know him personally, our daughters are friends. What do I do - offer him money for a new pedal (about £70 and a big chunk of the price he paid).