Maybe this is simple but I'm really pulling my hair out.

I have a Quick Draw that scores an additional 400 points (always 400) for players 1 and 2 (almost always 300 points for P1 and 100 for P2) when the ball crosses the player/ball advance switch in the trough ONLY if the scores are over 10000.

Or to put it another way...
Start game
Score 11000 points (before or after bonus collect)
Drain ball
Collect bonus
Ball passes over trough switch
Player/ball advances and 400 points score across P1 and P2

If I play through all balls with under 10k scored there's no problem. The game also advances through a single player or 2 player game normally. I've found and eliminated a number of issues with this game including AX/BX relay troubles, non working bonus stepper, player advance issues due to a out of adjustment score more switch stack and probably others I can't recall but this one has me stumped. TIA for any troubleshooting help on this!

Oh wow, thanks. Amazing what searching for the right (or wrong) terms can (or can't) yield when troubleshooting. I'll try this stuff out and close up this thread if it works.

Edit: doing nothing but adjusting the trough switch to be right on the edge worked great. Played through a bunch of games and no issue at all.