Here you go buddy for a simple fix.
You need 17-18 and 41-43 ball switches.
You can unplug all playfield harnesses. While in switch test mode-Alligator clip the driver board (one at a time to match photo) to verify your board is working for said switches.
If board works plug only circled playfield plug in since that is your switches. Make sure the underplayfield plug circled is solid (not likely the problem since lower switches would still work anyway) since that’s a connection to upper playfield switches.

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So it’s definitely the board/boards. Sounds like a bad chip or maybe the 40 pin connector. Try pulling board apart and connecting back. Test and if improved you probably just need to replace 40pin connectors. Again make sure the two switch connectors are unplugged from board while testing to isolate the playfield. You can go into switch mode and start pushing on chips and the 40 pin connector to see if something helps. Maybe something is loose.
If no improvement search forum for system 7 switch issues.
Ksarcade has the sys7 mpu swimmer board for 199. Assuming your driver board is good your done. You could sell your mpu to someone that fixes them. Unless you like working on boards, the 199 mpu sounds like the best option.

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Does it test ok with the jumper wire on the board?

Is switch 17 a reed switch or micro switch?

For targets. It’s usually;
1) clean drop targets with novus 2. Make sure they slide down when tapped.
2) switches may need to be cleaned and adjusted so they register. This can be tested in switch mode as well. I know one of mine had a broken diode and wouldn’t register.
By the way I like these decals someone on pinside made.

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