Quoted from Rikshaw:
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.
Just checking but did you remove the diodes from the circuit when you checked? You need to do that.
I had a similar but not the same issue with my Special Force. Turned out it was a short to ground. Also, I was causing it by leaning on a rail while I was pushing a switch. I’m not saying you are causing it, only that it might be a short to ground that you should check for in the circuit.