OK.

So here is a video of the problem.

https://www.youtube.com/watch?v=SeALZMIaJ70

If you want me to video inside the box i will.
I was racking my brains this morning and i remember something similar happening on my previous machine when jogging.
Could this possibly point to the fact that my problems are possibly connected to the PC / mach3 driver / plugin?

Cheers
Martin