Starting with Big Guns, system 11 games had an additional "auxiliary power driver" (APD) board. This board was used to hold the:
Bank select circuit and bank select relay.
Bridge rectifiers that supply the solenoid power (previously these bridges were just bolted to the back of the backbox).
Driver transistors (TIP36) for the 50 volt devices. This eliminated the small relay boards under the playfield. Up to eight TIP36c transistors can be used on this board. But if a game didn't use all eight, only the number used was actually installed!
Coil diodes. The coil diodes were no longer mounted on the coils themselves, but were instead installed on this board. This eliminated diodes breaking off the coils due to vibration. It also simplified coil replacement, as the operator no longer had to worry about which coil lead the diode's band was attached to on the coil.

Did you check that the wires have continuity?
Not broken somewhere in line.

And I don't have the schematics. But is there a relay associated with the targets? Maybe a cracked solider joint. Or just failed.