These 16 switches on the Player unit control which player receives scored points.

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Do the Player Up lights light correctly or with the erroneous scoring?

Are the 16 switches in my earlier post working correctly when this happens?
https://pinside.com/pinball/forum/topic/gottlieb-jet-spin-1-player-game-scores-points-for-other-players#post-5340765

In that case, it's looking like the switches in my first post are working OK and the problem is getting the Player Unit solenoid to fire 4 times.

The problem is probably in the area frenchmarky circled in his post or in the coin unit to the right of that.
https://pinside.com/pinball/forum/topic/gottlieb-jet-spin-1-player-game-scores-points-for-other-players#post-5350316

If you'd like to try a phone call, send me your cellphone number in a private message and I'll make a first reply with a text message.

Since you're still posting here, did you check the switches I suggested inmy post 37?
https://pinside.com/pinball/forum/topic/gottlieb-jet-spin-1-player-game-scores-points-for-other-players#post-5350580

From the last page of a Gottlieb manual (this one from Top Score)

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Yes

After I asked him to pay attention to the pattern of Player Unit solenoid misfires, the actual Jet Spin owner ( Kevlar51 ) emailed me this description:

I played through 12 single player games and watched/listened to the Player Unit solenoid. Each time that a score went to the wrong reel, the solenoid would fire-fire-stutter/fire-fire. Meaning the third firing was abnormal, but there would still be what I'd consider to be a normal fire at the end.

That narrows down the problem to this leg of the logic. So the next step is to attach an Alligator Clip Jumper across the White-Blue to White-Brown on the Coin unit disk and see if that eliminates the Player Unit solenoid misfires.

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