Alrighty, confirmed that the 50v fuse was blown on F5 on PPB. Replaced with CN2 on Flipper Board plugged in. Blew the fuse on power up. Replaced F5 fuse again, unplugged CN2 on Flipper Board, powered up and immediately blew fuse.
Per the link I mentioned above, seems this indicates there's a problem with the other coils' circuit, not the flippers.
My next step is to remove connector J8 on the PPB, the return for that circuit. If the fuse still blows there's probably a ground short somewhere. If not, there's a problem with a coil, diode, or transistor most likely.
Edit: I disconnected J8 and the fuse did not blow - probably no ground shorts. I'll pull the PPB and test Q4 transistor. Wiring at coils looks good at first glance, but could definitely be coils or diodes causing the problem as well.