Z axis and Z probe issues

My x-carve 1000 has developed a fault associated with the Z axis.
Symptoms - during a carve, the Z axis was operating normally carving a 2.5D circular badge 45mm in diameter. Part way through the first pass, the Z axis seemed to move down with each pass in the X direction until carving through into the waste board. I abandoned the carve and went to restart on a clean work-piece.
Now, as I try to set-up, the probe does not work, saying the probe is plugged even when it is not plugged in. Connections checked and just in case I run the machine set-up. The set-up works until it gets to the probe settings where it goes immediately to accepting the probe is plugged in even though it is not! Same situation after I remove the probe connection at the x-controller. When I try and operate the machine using manual setting for the z-axis, the following happens. The machine raises the z-axis, moves the x carriage noisliy towards the carve start point and then the Z-axis is driven down very slowly in small increments, after about 25 seconds, the bit reaches start depth and the cut commences in x y and z directions. after the first pass, ( 6 passes in all ) the same 25 seconds of slow mivement before the next pass then continues. ( X and Y ) are both stationary whilst the z moves towards the start depth.

Anybody with any clues?, I think the controller is faulty but am ready to be corrected.

Checking your wiring. Something may be grounding or loose.