Bit of a daft place to fit a PA, you have to remove the PA from the wall to check anything inside the keypad. this means any readings you have taken in your OP are likely from the keypad and not with a meter too.
It's also not where the cable entry is on the keypad you have made your own hole in the casing, it's unlikely but the PCB of the keypad maybe pressing on the cable causing an intermittent mystery resistance via some keypad component.
I would say if anything the resistors are clamped too tight up to the ceramic this is where they are weaker and more likely to break. You could easily wire that double pole at G2 and job done with no discrete components flapping about inside.
As for the PA in question I don't use them so can't comment but i would be inclined to use something more modern style, reed switches in PA's are so last century...