I had to put a small washer or 2 under the cam optos when assembling my MPF to raise them higher.

The opto interrupter cam worked but not all the cutouts covered the opto beam completely. and it couldnt find the home position.

This led to a similar condition that you describe:

Working but not finding the home position and getting bad CCW messages on a new 10 opto board.

Raising the cam optos "up" a bit with 2 small washers under the opto plastic housing at each screw got the opto beams covered sufficiently by the cam. I had to get slightly longer screws to get them to bite properly.

Maybe this is part of your issue.

I documented this in the doctor who thread.

Removing the MPF is not as hard as it seems. There's only the forcefield plastic, the forcefield, and 4 machine screws holding the whole assembly in.

Dont be afraid of it, most of us can remove it in 5 mins or less after having done it many times.

Whats nice about this is that you can set it in the bottom of the cabinet with the playfield all the way up.

Plug in all the connectors and test it thoroughly before reinstalling it.

People usually just search the club thread for my posts.

Is sounds like someone in the past had replaced the MPF frame.

This causes the cam optos to be about 3/32" low.

Please read the club thread about the 5 opto board problems.

Im hoping that DumbAss will make up some good, working boards to have here in the USA.

Unless you are doing a full ground up restoration or working on a pristine game, the linear problem solving system (though good) is very tedious.

Hacked and rebuilt parts from the variety of vendors, plus weird route fixes and patches leads to troubleshooting nightmares.

Way too many variables to add to the equation.

Things are more dificult than they otherwise would be.

This is where experience and pinside shine!

DumbAss had it right as a mechanical problem if everything electronically tested out.

Pinside is an awesome reference for unhacking games.

Case in point:

I spent a week solving a thing flips opto on my TAF.

Everything worked yet nothing worked.

It ended up that the prior repair person had accidently soldered the Rx opto wires in reverse.

This causes the opto to work, but be very weak.

The opto pair would only register if they were physically touching.
They would fail if they were 1/8" apart.

Once the wires were correctly installed, it worked perfectly.

I found the solution on pinside!

Theres only 2 wires, but theres and emitter and a receiver (collector) inside the plastic lens of the opto LED (C and E on the board).

There is a big side and a smaller side if you look into them under a light. So, yes they can be wired backwards and still work very weakly.

Properly wired the opto works powerfully and perfect.

If the wires are reversed the opto will be weak and only receive if the transmitter is literally touching lens to lens.

This was discussed in another thread with exactly the same problems I had. Homepin suggested turning the opto 180 degrees, but its much simpler to just reverse the wires.

The guy that had the problem was dealing with it for 18 months until a solution was found:

https://pinside.com/pinball/forum/topic/tech-optos-works-when-close-but-not-from-far#post-6866079

Homepin thead on optos:

https://pinside.com/pinball/forum/topic/how-to-determine-the-c-e-of-black-opto-receiver-leds#post-3538582