I experienced this very recently at the PHOF in Las Vegas. The gentleman on staff had to repair an issue that lost me a credit on TOM. He ended up putting 5 on there for me by accident. He smiled and handed over the machine. I collected a few additional credits and got tired. Left the games to a few really happy kids.
I proceeded to play my fill of Pinbot, Space Shuttle and then some TRON LE and BDK. I had some great games on all of them and ended up leaving credits behind on a few more!!! Good karma? maybe