In my experience, which is limited, I've found that cleaning each and every score wheel mech, stepper, and contact first will provide you with a much better idea of what is really going on. So if you haven't done that, you have a few hours of work ahead of you.

Good luck. There's nothing like getting a few flawless frames in a row and hearing the bells and click-click-click-click!

Try to buy a manual for the bowler. It will show mechanisms at home position, along with other things that a schematic won’t tell you!

Clear legible images of the player stepper coils and score motor parts of the schematic would be helpful.

/Mark

As already mentioned, first cleaning the score reels, step ups, snugging up the switch stack screws before
adjusting, ect. is always a huge plus..
I expect the mark (probably yellow) is still on the score motor's cam. It should be at the 12 O'clock position
when it's at rest. This is the zero position. The pin reset motor should still be in motion after the score
motor comes to rest. This is so the Bank Relay resets (which is toward the end of the score motor's revolution)
before the pins reset.