Sounds pretty common I get calls years later the machine you sold me isn't working its been in storage since I bought it plugged it in and it doesn't work what are you going to do about it.   I normally just laugh

WOW  

I actually have a funny non pinball related one of these, a friend of mine sold a house and five YEARS later the guy who bought it tracked him down and contacted him complaining the element in the oven had died and he wanted him to pay for the replacement.. ROFLMAO

I would have told him to f%^&K off when he tried to re-negotiate over the phone.

Good advice for the future, seems it would have saved a lot of hassle