Many thanks for the replies everyone.

I have however bought a switch based z height sensor. I got one from Sorotec but opted for the slightly bigger one with 14mm button.
It has immediately solved the problem, I wired it in and it showed up in the diagnostic screen when pushing the button.
I had to edit the m31 macro to active switch ( true mode )and do a few repeat tests to get the exact switch activation height after getting it close with a caliper.
Have used it quite a bit so far with no problems and very good accuracy.

I understand there is likely still some kind of electrical interference going on and one day I would like to go over everything and build a nice professional control box, but for now it works well and I can keep learning on this machine.


Ollie