Sorry for no responses on this yet. I pulled the driver board out of my machine last week and replaced a bunch of transistors and resistors as preventative maintenance and haven't had a chance to test out the suggestions. As part of my maintenance, I heated up all the solder points on the 2J2 and 2J3 connectors. I'm assuming this is considered "re-flowing" or do I have to do something else? I did check continuity with each solder point and corresponding male pin to ensure that I didn't screw something up.
As I mentioned, every other element in the game is working properly so I don't think it's the 2J2/2J3 connectors otherwise I would have a bunch of other stuff not working.
I will check Q10 and the orange-green wire on 2J13 (pin 8). I guess as a proof of concept, I should be able to short the orange-blue wire on 2J13 (pin 9) and the left kicker should fire. When connecting to ground, can I just attach the wire to the ground strap of the machine? Is that sufficient?
From what I understand, the two switches on either side of the sling are what trigger it to fire and count the points. I've looked at all the wires on the coil and the switches and everything looks normal.
I will test and check back in ASAP.
Thanks!