Thanks for your help andy - I understand the switch theory but are we saying that from the shot below that the square will indicate that the opposite diagonals in this instance would be switch 71 and 68, 71 and 67 and 71 and 66 as there are potentially three squares ??May well be a red herring. But you're missing the theory. You can make a square out of any two points on diagonally opposite corners of a square. From one of them go up or down to the row that the other one is on. This is one of the other corners. Do this for the opposite corner.
We've established its not the shooter switch so you need to test the others that come into play. Ie the trough and out hole switches.
You also look like you have a rogue switch on the coin inputs on the left hand side. I can't see how this will cause issue, but worth disconnecting any coin mech.
