Keep going Rob - Process of elimination.

It does not seem to be a stuck switch. I've seen similar problems before. What your need to do is take out the tens and hundreds score wheel and tighten the switch stacks with a flat head screwdriver (with the game off). Clean the contacts on each reel stack with a business card.

Start a game

Do all reels reset to zero ?

Does the ball get served and no score added ?

Hit a tens switch - what happens ?

When it gets to ninety, hit another tens switch - What happens ?

Hit a hundreds switch - What happens ?

When it gets to nine hundred, hit another hunderds switch - What happens ?