Picked up a very nice, fully working Bone Busters the other day. Game was working when loaded. Something must have happened in transit because now game will not boot. I get a Slam Switch Closed error. When I remove J6 from the MPU in the back box, the game boots properly, which leads me to believe that the issue is with something connected through J6. The slam tilts sure seem perfectly fine, and I get the error even when I disconnect the slam tilts. My next step was going to be to work through every wire (every switch) that is connected through J6. If you have any tips to help me get rolling on all cylinders, I'd sure appreciate it.

Anyone have a list of what runs off of J6 from the MPU connector? That would be a huge help. Thanks.

Looks like the issue was a bad regulator. I was chasing down the error. Rookie move. Instead, my local pro came over and noticed that the 5V was dropping and that was the issue. Fixed the regulator and seems to be just fine.
So, if you're getting an error on this style of game, don't necessarily chase the error before you've checked your basic measurements.