My dad has a project taxi he is working on and has had the boards professionally looked at and repaired. Everything on the game seems to be working fine other than several of the playfield coils are firing when certain flashers are going off. The work fine when they are supposed to, but they also fire when flashers go off. Different flashers seem to affect different coils. For example, when the flasher under the Santa insert flashes the center drops reset coil pulses with each flash. The pops and slings seem to not be affected by this either, only the knockout holes, catapult and the drop reset coils. As you can imagine the game goes bonkers when you get a jackpot with every flasher on the playfield going off.

Any idea what could cause this. We have also tested with another working MPU out of an F14 and the same problem persists.

That was it, thanks!

Yes on the aux driver board. One side of the relay had fused together.