Probably a dozen times after selling someone a game I’ve had this complaint.
Always pisses me off. I’d I knew I’d have just removed the knocker and kept it, there’s like $30 worth of parts in that mech!
Once someone called me frothing at the mouth over the loud noises their pinbot is making when they turn the game on (they simply hadn’t made a ramp shot in a week).
Now I always turn off the service knocker feature on those games.