Small update, I could not work out what was causing the fault, after trial and error I decided to replaced the switch matrix chip just too see what would happen. Replaced the
ULN2803APG as I had a couple of spares. Fault has gone and plays as it should now.  I ordered sum new micro switches and diodes for the ball lock just to be sure.
No ball lock issus now, fingers crossed...
More fun to fix than to play sometimes.


Pinpal..