Hi All,
Sorry for the delay in getting some data back.
So I have carried out a series of test, mostly concentrating on the Z axis, but the issue is present on the X and Y as well.
Firstly, I measured the voltage at the main input, this was 248 - 249v
Next, the voltage going to each driver was 68v (There seemed to be no drop under load)
So I stripped out the spindle driver and re-ran the position test. Work Piece Zero went from Zero to -0.7969mm (which I think is what you class as gaining steps??)
Next, I stripped out the motor driver that drives the 4th axis (not used it yet!!), as well as disconnecting all leads that go to the front panel.
Re-Ran the test and Work Piece Zero went from Zero to -1.4781mm (which in machine chords was -217.3669 started and finished at -218.8450)
Final Test was pretty much down to bare minimum. I stripped out all the drivers except the Z axis. Removed all power lead not in use. Disconnected X and Y Limit and Home switch (kept Z connected)
Re Ran Test and Work Piece Zero went from Zero to -0.8206mm
Below are just some extra photos I took of the electronics if of any help