The switch with the missing white-blue wire is the End Of Stroke (EOS) switch for the Score Reel. When a Score Reel should advance its point relay (10 pt relay in this case) fires and closes a switch that sends power to the Score Reel solenoid. The point relay stays closed until the EOS switch on the corresponding Score Reel opens which cuts power to the point relay, and in turn, the Score Reel solenoid.

The EOS switch is there to make sure that the power to the Score Reel solenoid doesn't cut until the Score Reel plunger has pulled all the way in. It's a feedback mechanism to make sure that just the right amount of power is sent to the Score Reel and no more.

It sounds like your Score Reel plunger isn't able to pull all the way in for some unknown mechanical reason so the EOS switch never opens and the point relay never stops delivering power. Rather than fix the problem someone disconnected the EOS switch so that you only get a brief pulse of energy to the Score Reel while the 10 point target is closed. It can work that way but it's unreliable.

Once you sort out the mechanical issue with the Score Reel reattach the EOS switch and you should be good to go.

/Mark

There are many topics here about working through game reset issues. They should be able to offer some helpful background. It's likely that the game is perpetually trying to reset because something has indicated that it still needs resetting. Chances are that it's your Score Reels since you've been working with them.

Each Score Reel has two switches that operate when the reel shows a 0. One opens to prevent any more reset pulses from advancing the Score Reel. The other in your case closes to tell the DB/Reset relay that it has reached zero. Until all four of those switches close (electrically, not just visually) along with the Motor 2B switch in the DB relay circuit the Score Motor will keep running thinking that one of the Score Reels hasn't yet reached 0.

Nice to see you in this corner of the forum @mr68. Yes the online repair clinics are still happening as HowardR pointed out, every month or so. EM Repair classes too, but not as often.

You could jumper the orange-red wire on the wonky 10 point score reel coil solder lug to another, working score reel coil solder lug. (Like to the brown-red wire on the 100 point score reel coil solder lug for example.) Then hit a 10 point target. The two score reels should fire together since the score reels are sharing the very same pulse.

If you hit a 10 point target and the 100 point score reel advances without a problem you know that the issue is likely in the 10 point score reel and not in the 10 point relay or its switches. On the other hand if you hit a 100 point target and the 10 point score reel works then the issue is likely in the 10 point relay or its switches.

I don't understand what you did. If everything works I'd expect to see two score reels move together.

I see. A little clarification is in order. You've jumpered the Runout switches together on adjacent score reels. That can work but it's not foolproof. Have a look at the schematic:
Domino score reels (resized).jpg
The wires on either side of the Tens Unit Runout switch have the unfortunate wire colors of OR+RED and OR-RED which may seem similar but are completely different. (For wire color details see: https://www.funwithpinball.com/resources/Gottlieb-Wire-Colors). The other score reels have the same problem. Putting your jumpers on the Runout switch requires that you pick the right side of the switch: OR-RED to BR-RED.

If you instead jumper the coil solder lugs together (in the red box above, white box below) there would be no ambiguity:
Domino score reel solder lugs (resized).jpg
Once those two score reel coils are connected (careful not to short to the score reel frame) they should behave the same way since they're receiving the same electrical signals.

The reset circuit for the 10 point score reel is in red below:
Domino 10 pt reset (resized).jpg
All three switches need to close to advance the 10 point score reel during reset. Since the other score reels reset you know that the Motor 1A switch is good. The issue is probably with one of the other two.

This is the carry circuit into the 100 point relay:
Domino 10pt carry (resized).jpg
Any time the M/10 point relay fires it will close a switch that will fire the L/100 point relay if the 10 point relay is in the 9th position.

Separate problems but switches on the 10 point score reel could explain both issues. The Runout switch in the first drawing needs to be closed unless the score reel is showing a zero. The 9th position switch in the 2nd drawing should close only when the score reel shows a 9. Both are located at the top back of the score reel. Use the wire colors to identify them. Compare how they work to the same switches on a working score reel.