Chris, here's a few thoughts that may assist or narrow down the problem?
I'd first isolate what is causing the problem, could be board related or play field related. With new boards it's unlikely to be a board fault, but it could be installation issues like Marty has mentioned. So disconnect switch row and col inputs and test the board side. Clay's guide has a description on how to do this with diagnostic mode and an alligator lead. I'd guess this will all be ok, but best to prove it.
With the playfield plugs removed give them a really good visual examination - I use a big magnifying glass. For a few bucks and an hour or so repin them, Same detailed close visual examination of all switches - you're looking for blobs of solder or whiskers of wire that are out of place. In desperation you could replace all switch diodes., but this is only really an issue for simultaneously closed switches.
In diagnostic mode with play field connected I'd repeatedly exercise the switch that are causing the resets and examine which switch shows up. If it's not the correct one that should give you some leads.
With a game up I'd fire all the solenoids a few time each, one at a time - if no resets occur I'd say this rules out power supply issues.
I take it you've got the game manuals? The firepower site
www.firepowerpinball.com has wiring diagrams and just use the switch matrix table in the manuals for equivalence.
In normal game operation does slam tilt cause a total game over, whereas pendulum tilt looses just a ball? I don't know but am wondering about the different resets going on?
Hope this gives you a few ideas.
