Still trying to find the time to get back to this .
I did check the diodes are all the correct wway around last weekend when I was installing the Snack bar mod .
Also noticed that switch 41 error has disappeared but the other 2 switch errors are still there .
Also have a new (probably unrelated ) intermittent issue of 'pinball missing' when trying to start a game when all 3 balls are in the trough .

Next step will be to isolate each switch and test