Dear God.
I finally sorted the Santum wall switch issue.
@SpiderPin msg me direct for some assistance if yours ends up being the same pig as mine.
Basically this was what was happening.
The actuator arm in the mech flicks up to reset the wall. Nothing holds it up there it just comes down by itself. The gravity swinging the arm back down ended up hitting the microswitch arm which then closed the switch causes error 51 switch error I had.
I first changed the microswitch as the metal arm was nackered.
I cut the metal arm a bit shorter and had it so the end lipped at the very bottom.
Also f*** soldering these things so god damn fiddly!
The issue still happened as soon as put the playfield down the arm would come down and cause the microswitch to activate.
You have a screw at the bottom of the mech which you use to adjust the actuator's arm.
I also found WAY too much greese on that arm its was basically flopping all over the place. I reduce to the amount of greese and then used a small felt/foam pad.
I drilled a hole into the pad and screwed it onto the screw in the mech. This now acts as a cushion for the arm when it falls naturally due to gravity but can be manipulated enough when the arm/wall comes down and squashes it down enough to make contact with the switch.
I now see why everyone says The Shadow is the worst pin to maintain!
All seems to work and I have pads galore if it ever becomes worn I can just repeat the process.