Z axis error woes

[Jonathan]

Yes Machine setup was my first thought Jonathan but the leveling of the bed rules this out.! Not sure the pcb would be so consistant increasing thickness.?

Yep, the PCB itself has good thickness tolerance so I was more thinking the PCB itself might not be stuck down flat, but as we both said... that makes no sense! Maybe the gantry slipped at one end? Again unlikely.

I doubt it's the USB cable as interference or interruption in the USB signal would cause all sorts of problems, not a nice linear error. Similarly if the motor is connected wrong it'll either break, not spin at all or spin the wrong way.

Out of the causes you suggested I think the acceleration setting is the most likely cause as that could well induce a consistent error. Testing on a different axis, or even probing a grid so we can plot a plane is also a good plan.

Try running the probing routine exactly as before, but twice in a row ... probe from Y0 to Y10, then start again at Y0. If the two point lists are virtually identical you know it's not a motor or motor tuning problem as those problems would make the second probing routine output different to the first.

I feel for hank because things like this can drive you crazy.!!

Yep.