I've been spending almost 2 days looking over all the switch diodes, and trying to figure out what's causing this, all diodes test .5v +- 10% on all switch diodes. And 0 in the other direction. I added a picture 20210401_105629 (resized).jpg of the switch diode in case I reversed it, but it's situated like all the others, with current flowing from the white wire to the other side of the switch.

If I disconnect switch 15, the trough (ball#4) works fine, and doesn't cause anymore headache, no other issues on the playfield, except the dot on the droptarget coil/switch, which is a given as it can't see the target's state because the switch doesn't fire.... Here's me manually manipulating the switch (the deflector panel is on because the playfield is up) :
https://photos.app.goo.gl/PCeUMCbS9ysZUyd69
20210403_192522 (resized).jpg

If I had issues with another switch, I think I could figure that out, what boggles my mind is that the two systems are in my mind completely un-related as the trough is bound to the opto board below the playfield, and the switches are all coupled to the power driver board. I mean there must be a correlation, it's just not what I'm used to seeing. I mean it is strange that the opto and the switch share the same row, but again in the wiring I can't find where they share anything. Sorry the schematics had a lot of mold or mildew whatever on them.
20210403_192451 (resized).jpg

Is this "Common" on a RFM? To have switches interfere with opto boards?

Cap looks solid
20210404_110109 (resized).jpg

Measures good:
20210404_104825 (resized).jpg

Board looks good:
20210404_105934 (resized).jpg

I have a little rust on one of the resistors, all measure @ 270ohm +- 5%
20210404_110023 (resized).jpg

So, wow what a difference a week makes... I was about to post this update when the server went down....

20210404_143654 (resized).jpg
So this is how it's "Supposed" to be, or works as intended, for some reason it's backwards from all the other switches, with the NC side getting the voltage, and then depending on the switch it closes when the drop target is down, and opens when the drop target is up.

Either way it's fixed and the trough and the switch work harmoniously now.

In My defense when I got the machine it had just two wires soldered like you saw the first picture and no diode, so... it obviously had some work done on it, and is now much better...