NOBODY follows rules. I don't like when kids start games and walk away or start a game on a different machine before they finish. It gets too loud with no good reason.
Who cares if they restart a game after a bad first ball? Sounds like you are metering play count on your machines. There is no reason to, condition is king when it comes to resale, not play count.
Oh, no picking boogers and wiping on the machines. That is all.