Quoted from delt31:
if someone knows how the power shed at least works (e.g., what is the switch that causes the S to be registered, I can use that info to find out my problem so even that would be helpful
I just ran thru the JP switch diagnostics:
1. Powershed trips switch #60 in the subway << this is the one I think may be the issue
2. TRex gobble trips switch #59, also in the subway
From your description, seems like nothing else in switch matrix column 8 is out (flippers ok, VUK working, etc.) - which is a good thing (I recently knocked out a switch matrix column - everything in that column was non-functional - turned out to be a tiny transistor on the CPU board, easy fix).
I still lean toward the diode on Switch #60 as the probable source - just sounds so familiar to the issues I had on the Control Room diode, even if the switch is otherwise functional.
Do you have any spare Diodes? Might be worth cutting that diode out of the circuit, test, then replace. On a good diode, you should see ~500mv across the leads in diode mode on your DMM, black lead at banded end. If it's good, then you've wasted ~$0.05, if it was bad, then you have your solution.
Hope that helps