Ok - I thought I would put some closure in here..... The random X and Z axis ' jams' were 100% due to electrical interference from the spindle control wires.

I had unshielded control cable, with shieleded stepper cable

Then I tried shielded control cable but mistakingly placed the machine earth inside the Spindle power cord, and in doing so charged the entire machine up with a generated AC signal.

Then I earthed the frame + spindle + spindle shielding + stepper motor shielding seperately to house earth, and finally, no issues !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!