If the U20 IC was not socketed and you replaced it you may have pulled a trace or pad breaking continuity. It's also possible that there was alkaline corrosion that just reared its ugly head. With switch matrix issues the first best step is to isolate the board from the playfield. Once you know where the problem is (board or playfield) you can then try to find it.

If you post a picture of the board (high resolution, well lit and in focus) it might shed some light.

If the problem is minimal it might be cheaper to repair the board rather than replace it. It depends on the condition of the board. If you do end up deciding you want to replace it I'd be glad to be able to provide a board for you. I just completed two boards and they both passed on the bench (verified).

Yes. If you do the Pinwiki jumper test for the pins between J207 and J209 and not all the switches register then you have a board issue. This is because you have isolated the playfield wiring by doing the jumper test.

This is not a negative comment against the person who did the work on your board but whenever I assess any board the first thing my eyes go to is any prior work done on it. The U20 IC (ULN2803A) is responsible for the column drive (grounding the switch columns). It is the place to look when you have switch column issues. It is also required to not just look at the IC itself but also the ancillary supporting circuitry.

Blow this up in your browser and use it to buzz the connections indicated for the columns that are inop.
Like @dumbass, I would be suspicious of the work that was done to the board. The traces at some/most U20 chips are delicate and can be ripped easily. The strobe signal traces are on the same side of the board as U20. You probably won't be able to visually inspect those traces as they will be under the socket (I hope he used one). But you can easily buzz between the pins of U20 and the next component.

https://www.pinwiki.com/wiki/images/e/e7/WPC-089MPULayout.jpg
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Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact ... for board repairs
http://www.PinWiki.com - The Place to go for Pinball Repair Info

U20 pins 16 and 17 should buzz to the bottom of R69 and R68.
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Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact ... for board repairs
http://www.PinWiki.com - The Place to go for Pinball Repair Info

OK. Let’s keep testing for continuity all the way to the header pins. Perhaps there is corrosion under J206. I see that fairly often. Use the PInWiki diagram to complete the buzzing.
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Chris Hibler - CARGPB #31
Http://chrishiblerpinball.com/contact
http://www.PinWiki.com/ - The new place for pinball repair info

OK. You can send that original to me if you’d like. I’ll repair it and add NVRAM. Happy to help.
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Chris Hibler - CARGPB #31
Http://chrishiblerpinball.com/contact
http://www.PinWiki.com/ - The new place for pinball repair info

OK. Happy to help though. Any time that you are ready.
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Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact ... for board repairs
http://www.PinWiki.com - The Place to go for Pinball Repair Info

Donate it or get it repaired and post the findings here. I would like to know what is wrong with the board.

Ken.