I'd start by taking a look at the Tilt relay. Is it pulled in all the time? If so, there are 3 things that power it on the schematic - the tilt switches, the inertia tilt and a timer unit switch. I'd also check the shutter motor cam switches 4a and 4c and shutter motor carryover cam 1b.
Shutter motor switches can often get tweaked if the playfield isn't lifted carefully.