Thanks for the reply Komatias. The couplers are nice and tight, so they're not slipping. Though it does need re-wiring. So I'm probably best starting there. Can you recommend a good supplier for the cabling - and maybe someone in the Sheffield region who could sort it if it's too bigger job for me?

And yes, I love that little controller. Really easy to operate: set the start point, load the code from SDcard and hit run. I really should go the Mach 3 route though :)