Every now and then my River Boat would just go straight to tilt mode and end the game while playing. I was at my wits end trying to find the problem when I discovered this. See pic. A screw broke off a part on the playfield and landed perfectly into the gear box of the score motor, which, back then was not covered. So every now and then it would bobble around and jam the score motor causing the tilt. Just thought I would share showing some of the crazy things that can cause major problems.