Put the machine in switch test.

Pull the connectors off driver board 2J2 and 2J3.

Using a jumper wire connect one end to pin 1 of 2J2.

Touch the other end to each pin of 2J3 - note whether or not each touch registers only once.

Then reverse, pin 1 of 2J3 and touch each pin on 2J2.

If the board passes this test, the problem is on the playfield/in the harness.

If not, since it's not limited to a specific row or column I'd consider the PIA as a problem, though it would be best to check with a logic probe and the test ROM.

viperrwk

Could be a combination of faults between IC15-18. Test ROM and logic probe would help. Assumes all previous work is good including 40 pin replacement.

viperrwk