Just replace the opto (Switch 55)
Sometimes a weak opto can cause strange behaviour but still work fine in switch test.

Never mind error message. They are not errors, but a reminder to check for proper operation.

What works by manual testing? Are failures permanent or irregular?

TP3 on powerdriverboard must be 12Volt but it looks more like a broken wire at the moment.

Start with testing a working switch on Row 5, switch #25 'top lane left'.

If this one is working, there might be a broken wire in the chain of WHITE-GREEN.

Best guess - as already mentioned - is a semi-broken row wire down the line. The roll over switch that works is indeed the first in line. I think.

A broken wire may be invisible. Troubleshooting with a jumper wire run from the good switch is your friend.

Try to (gently) pull the wire where it goes in and out of a crimp connector. It might break off.

As mentioned, it's something on the row. A bad diode on a switch or broken wire. There should be a thread somewhere about testing diodes. Test the diode on each switch in the column. Go on aliexpress and order a ton of diodes. I think I got 100 of then for like $5. That way you have them for future.

Checked it out. 1000 for $7.
https://m.aliexpress.com/s/item/32813239398.html#autostay

100 for $1 shipped. How do they even make a profit at this point?

https://m.aliexpress.com/s/item/32422507038.html#autostay

When faced with a wierd switch problem on wpc look to all switches in the row and Column. Look for backward diodes that has been a bitch to find in the past and results in very wierd game behavior. Last resort replace all diodes in the row and column. Or swap CPU boards with another game. It may lie in with a bad chip U20 (I think that's the one I'm not at home so I can't look it up). You also may want to swap the opto driver board that can cause opto issues as well. Good luck let us know how it works out.
Regards
Al

Step one: Unplug all switch wires along the bottom of the MPU board, except the direct ones so you can still enter service mode.

Is the fault still there? = problem is on MPU board

Fault has gone = problem in the wiring, connectors, switches or diodes across them - equally, could be a fault on the 10 opto board as it connects to the switch matrix. Unplug it to eliminate it as a possible problem.

This is a simple issue but it does require a methodical approach. Don't just dive in and start replacing things willy-nilly. Work through the issues logically and step by step to isolate the problem.

Could you please specify which ones are "the direct ones"? Seems a bit ambiguous to those less experienced (myself included here).

Yes, sorry about that - I didn't have an MPU in front of me earlier.

The direct switches connector is the bottom left one on the board, J205.

Disconnect the others along the bottom (J206,7,8 & J212), up to 5 plugs depending on the game, and then all playfield switch matrix wires are disconnected from the MPU.

This is the bottom of a Homepin MPU (we clearly mark the connectors).

mpu (resized).jpg

Basically what he said. This should be easy to fix. If your errors are on Row 5 (15, 35, 55, and 65) and you don't have an error on 25 or 85, I'm willing to bet you have a broken wire on that chain of switches. Take a close look at Switch 25 (Left Top Lane) and 85 (Left Ramp Diverter) and see if a soldered wire broke loose from the switch. If no luck, look at each switch in the chain 15, 55, 35, 65 and see if a soldered wire broke loose from the switch. You can also check with a continuity tester or ohmmeter to figure out where the connection is broken. Normally, you should see continuity on the white-green wire to all 6 switches on that row.

Maybe it's time to send your MPU out for checking or repair by an experienced person? There are several that are active on here and it should be a very cheap/easy fix for this type of issue.

The positive thing is you have corrected a wiring issue and narrowed down the problem to 'probably' the MPU.

Could you post a picture of the MPU board just so we can see if there is anything you may not have noticed?

Do you live in the USA? If so I was going to offer installing a NVRAM that included part and shipping it back for $22. Yes, it does looks like that wet area might be corrosion, but also could be flux residue if the battery holder was changed. Kind of depends on whether you can tell if ran down the battery tab or not.

Send to Chris Hibler here on Pinside. He knows his stuff and did a fantastic job on my Johnny Mnemonic mpu board.

The turnaround time and "knowing it's all better" is well worth his rates, which are VERY reasonable.

Using the jumper test on the MPU board successfully for each switch rules out the MPU board.
Either the 10-opto board has failed or, perhaps more likely, the row or column wire that is daisy chained through an IDC connector on the 10-opto board isn't making contact with the conductor in the female housing.

Time to get those batteries off the CPU board. Love never dies, but Batteries always leak!

--
Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact
http://www.PinWiki.com - The Place to go for Pinball Repair Info