I have an odd issue with my Bally Eight Ball Champ. The center drop target switch will not register if either of the 2 left drop targets are down or the upper right target is down. The center target registers fine unless one of those other 3 targets are knocked down. I notice that the targets are all in the same column in the switch matrix, but other switches in that same column do not seem to have an affect on the center drop target.

I've looked at all of the wiring attached to the 4 affected switches looking for odd shorts and broken diodes. Also checked all 4 diodes with a meter and everything checks out fine. I'm a little stumped on this one.