It might be irrelevant, but let me point you to my own thread here: https://pinside.com/pinball/forum/topic/firepower-playfield-problem

I had a problem with the switch matrix driver on IC17 constantly frying, leading to problems fairly similar to yours with random switches triggered and lamp pulsing. The problem turned out to be bad isolation between the coil bracket on the pop bumpers and the lamp lead, so whenever the pop bumpers were lit simultaneously to a ball hit, there was a short. From what I understand some Firepower playfields have plastic tubing in this area, others don't. Mine didn't. Ever since I isolated the lamp wire I have not experienced problems.