Greetings,
Not sure i'm even qualified to ask the right questions but here it goes.
I have a (new to me) vintage Coin Operated Marvel Shuffleboard score board.
Issue: Neither of the Red push buttons activate the Red scoring stepper... UNLESS I push and hold one of the Blue Scoring Push buttons.[Of course this means every time Red scores...Blue gets a point; which doesn't seem fair)
Blue works fine on its own though.

So I think it has something to do with the common wire (TBH: I barely know what that means).
I'm looking for help from this community in understanding where I should expect the related wires go (there are so many tightly packed little wires to follow) or at least which wires should I be tracing to see if I can spot something disconnected, dirty, broken etc.

I've included an image with a quasi legend of the things I thought might be related or helpful.
(1) I think the common wire tracks to position (2) [I think]
(3) One of those white wires connected to the Blue scoring stepper coil is screwed into the cabinet (ground?)
(4) like the blue stepper...there are 2 wires connected to the red scoring stepper coil. (I don't see one of them being screwed into the cabinet like I do on the blue one.)

As you can see, and likely based on your experience with EM, the cabinet is quite vintage and is loaded with wires, i'm trying to minimize what i touch until I get better at this.

Can you suggest where I should look and what I might look for?
Great appreciated

Shuffleboard Button wiring (resized).jpg

Thanks very much.
I've reposted in the EM-arcade-games forum
Cheers