After the boards came back from repair the game boots erratically, playfield GI and lamps are out, and a good bulb in a GI socket flashes very bright and blows. Solenoids and flippers only buzz weakly. The meter shows about 35 V DC across the GI string, while board voltages test fine.

GI bulbs blow and solenoids only buzz: chewed harness shorting GI to coil power

Cause: Mice had chewed the wiring harness at the backbox connectors, so the GI circuit was shorted to the solenoid supply.

Checks

Measure the GI string on both AC and DC ranges; DC on the GI is a sign of a short to another supply.
Check for continuity between the GI wiring and the solenoid feed with the power off.
Inspect the harness and connectors where they pass into the backbox for chewed, pinched or bare wires.

Repair or replace the damaged wires and connector housings, insulating any bare spots, before powering up again.

Unplug the game before working on the harness; damaged insulation can put coil voltage on parts you touch.

Source: Pinball Repair help group!! (Facebook group)