Did you check the score reels and switch? from what i have read majority of the time needs a good cleaning and switch sometimes needs a bit of adjusting

The 10000 point scoring units for each player should cause a 100000 point relay to latch when it rolls over from 9 to 0. Pretty simple mechanism in the grand scheme of things - you'll just need to check the 10000 unit for player 3 and check this latching behavior. Probably either needs a cleaning (as suggested above) or something is botched/shorted/not contacting as intended and it's closing the latch path on 1 to 2 instead of 9 to 0.

This was just discussed in another post and as noted here in post 3, one of the sw. gap was too close.

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