The service buttons are not part of the game's switch matrix. I would back track and see what it was you were working on last and this happens a lot when people swap in LEDs with the game on and short something by accident using their screw driver or dropping a screw. Battery corrosion could cause this and the ULN2803 and LM339 chips are directly below the batteries on the MPU as shown here.

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If you don't notice any corrosion then check the common switches in the first column or third row I highlighted here.

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Hopefully the other switches that don't work all fall in either the same column or row and not scattered all over the matrix. If that is the case I would check the common wire under the playfield to see if maybe there is a break somewhere along the chain. If you have switches out in the same column check the green/brown wire or in the same row check the white/orange wire.

The next thing you could also try is re-seating connectors J206 and J208 on the MPU as well. I had switch issues on my TAF before and turned out I just needed to redo my J208 connector as seen in the picture here.

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Also if it ended up being ULN2803 or LM339 related I would get these socketed so in the future you can just pop in a new chip and you don't have to stress these traces again in the future.