Denford Software & Machines

I have a Triac with Next Move ST USB controller and the current VR Milling software. I am seeing what I think is a failure on the Z axis. Frequently the machine fails to home on the Z axis after connecting to the machine via VR Milling. The z axis position in the software increments continually (this is with the machine in the homed position for all axis). If I used the hidden home button instead I can move the X and Y axis but not the Z. Leaving the machine switched off for some time will temporarily cure the problem.

Does anyone recognise this issue? Am I seeing a failure in Z axis motor drive?
Also, are the driver boards identical on each axis? If so, presumably I can swap the board connections with another axis to try and narrow down the issue?

I have had the machine for a year now and have only just had the time to try some milling so this is quite furstrating....

Edward

Yes the drives are the same so you should be able to use the secret home button to narrow down the fault.

I was trying the machine again and a new symptom has appeared the spindle is descending of its own accord! No program running and no one near the keyboard. Does this point to a particular failure?

I swapped the cards and the problem moved to the other axis so I am replacing the driver card.