I have been chasing this for days and just not sure... I have a schematic, I do not have a service manual, but I do have a service manual for a "Chief" alley manufactured same time period and Im using that, very similar game. The 10-90 relay (relay on the right-green coil wrapper) is pulsing the correct number of times per strike (3)/spare (2) but the bell only rings once for either score. Switch #2 operates the bell. This happens in very frame except frame 5, that is my "Scores Double Frame". The bell rings correctly in frame 5 (4 times for a spare and 6 times for a strike). From watching the 2 videos (links below) it looks like switch #2 is not staying energized after the first ring. I am only saying that cause I am not seeing any arcing at the switch. Things I have checked are the 1-9 relay, Player Unit cleaned rivets, Score disc cleaned rivets.

Regular frame strike

Double Score frame strike

thanks
Steve