This is interesting...i dont think mine has anything there, does not seem stock. I had trouble (when no balls were locked) with 2 balls kicking out the trough when i first found my game. That first switch wire was bent up a mess from previous fiddling with it...sometimes it would slip to the side of the ball and not be registered causing the problem. I ended up replacing the wire with a new rigid one i shaped to match the others. Has worked perfectly since. Maybe there is too much room at entrance, and the ball could bounce off wall and come up into trough beside the first switch. The screw or nail tightens that trough entrance...hmm. Was this a service bulletin for the game?