Hey Kyle,

While I can think of some obscure reasons why you'd get that result when swapping the wires, at this point I'd start with simpler solutions like something else changed while swapping the wires around.

Are you testing the optos with a business card?

Is the thing assembly in the game? The reason I ask is the last little bit of movement that blocks the up opto is done by gravity. If the thing assy is not in the right position the opto won't close properly.

Not sure what this means.

Before we head down the complex path, just want to make sure you've replicated the result 2/3 times that when you switch the wires everything works.

I know it's a pain, but I've screwed myself before by not double or triple checking something like this. Especially when it gives such an odd result.

Next I would check the voltage at the optos and check all your voltages on the opto board.

If all that is good, I would say you've either got resistance in the wiring for switch 85 and/or a weak component in the 85 circuit. Check the resistance vs 84. It could be that two weak points are combining to make 85 not work and when you switch the wires you separate the two weak points and things work.

Based on what you've tried I would suspect the thing opto circuitry if it's a component. I don't remember what's on the board, but check resistors and anything else you can.

Also, what does the switch levels continuously cycle mean?

One other possibility: the metal tab that blocks the opto is not rotating fully into position. Typically the last little bit of movement needed to block off the opto is provided by gravity rather than the motor.

While it's out of the game hold it in different positions and you can see how the thing arm (and therefore the metal tab) will rotate around as it's held at different angles.