Have now re-installed Mach - no difference..
Also tried another PC, although it is a pretty low spec laptop (setup as a standard PC) - no difference..
Going to rewire my nema 23's (3Nm) in bipolar parallel today, not sure if I will be able to do the same with my Nema 34's as they are 4 wire motors, just waiting on a bit of advice on that, unless someone out there knows how to do it?

Just want to say that although I have not got to the bottom of this problem yet (and neither has Karl, my sympathies dude), I am very grateful for all the advice given.. Checking so many aspects of my machine is a real confidence booster with the level of scrutiny it has had this week, I feel like several engineers have checked my work and so far, most of what I have done seems right and a couple of things I have been able to improve..

Steve..