The mill and parts were purchased from a model maker who didn't manage to finish the mill conversion, but I agree the copy of mach3 supplied could have been dubious. The version I am attempting to setup with I downloaded from newfangled myself, it is only the demo version as I wasn't sure it would be my preferred software and I just wanted it for testing purposes.
The limit problem I have i assume must be either a bug in my mach3 download or a fault on my breakout board, or indeed there is always the possibility of stupidity on my part