Every story has two sides. It seems like threads like this change a lot once we hear the other side, in this case we many never know since the buyer is never identified and they are likely not on pinside but this is from the OP's side of the story:
- The buyer paid the OP $7500 for a TZ that didn't work or has serious issues - "Against my recommendations that a newer machine may be more reliable and less problematic." Kind of sounds like the seller knew this game had issues.
- Payment was made by credit card through PayPal F&F. The PayPal user agreement explicitly states F&F is not meant to be used to pay for goods and services. Not really surprising PayPal doesn't want to get involved or eat the loss on this.
- The OP told them "the next time I was near him I would stop by for free to fix the machine." Sounds like that never happened.
- When the buyer tried to talk to the OP about it, he hung up on them and blocked them.
I'm sorry to hear things didn't go the OP's way, but it isn't that surprising.