bump. i'm at a loss, too

Are all those LEDs?

Everything else work OK? Switches, lamps, flashers when tested?

(nice looking pin!)

Yes, all LEDs.
Everything else works 100%.
In fact, when you test each individual flasher, they all work perfect with no interference with the coils.
But in coil test each coil seems to "backfeed" into the purple and brown flashers.
It really has us stumped and don't really know where to go next.

A bad diode on a solenoid or a faulty blocking diode on the PDB could cause this in a single case, but unlikely to occur in so many instances.

Make sure the ground side of the solenoid circuits and the flasher circuits on the PDB have good connections to ground with no resistance. Also make sure all of the PDB mounting screws are installed and tight.

I'm not getting what that would achieve. Plus if the diode was installed backwards across the flasher it would risk blowing the fuse, or worse a component. Same thing that happens when someone installs a diode backwards on a solenoid.

Did it start after switching to LEDs?

Tried installing a diode on the first and last flasher of the strand [band toward the thicker wires] and made no change in symptom.

Unfortunately, we didn't test it before we just tore it down completely for a new playfield and decals, etc. We played it a couple times before but didn't notice if the flashers did this, but wasn't specifically looking for it, either.

All screws on driver board are tight and have tried a repaired coin-op cauldron driver AND a brand new rottendog driver and both exhibit the same behavior. Pretty sure it's not a board issue.
Also made sure my outlet was grounded and properly wired [reaching for straws]

Can you make a picture of the powerdriverboard with everythinhg connected ?

Some connectors are difficult to see but all seems correct.

I thought there was a compatibility problem with rottendog concerning sol#23 and #24. Could you disconnect J125 and J126 and see if the problem stays or leaves.

Have you tried another CPU and/or ASIC?

My bad sorry! I stayed in a Holiday Inn Express before but that was a long time ago.

jwj - have not tried a different CPU. Can do that on Monday as the other 2 WPC games here both have rottendogs.
zaza - with j125 and j126 disconnected, the problem remains.

Did this ever get resolved? I have just restored a creature - received it completely trashed so never played it, now after resto its flashing every time a coil fires!

Are you using LED flashers? Try regular flashers first. If it works there.... get better flashers.

My theory on this is that the inductive kick that coils give up when collapsing their magnetic fields, while blocked by the diode, can cause spikes that get picked up by other wiring. This might be enough to light LEDs but not enough for the normal flashers.

As for a fix, no idea other than isolating the wiring as much as possible, which would be difficult since both flashers and solenoids share the same harness.

The game was designed to use #906 and #89 bulbs for flashers. Not LED's. Install the correct bulbs to clear problems.