Gday Hood, thank you for the assist.
I don't have a copy of the files I've tried, but its basically two lines crossed at 45 degrees, generated in Cam Bam and Lazy Cam, both demo mode, do have a license for Mach3. Will attached one later, but the venerable Roadrunner.tap file shows this behavior.
Travel direction: Its just the opposite of your statement. Running G code it will only go +X direction, not in the -X, but all other controls move in all directions
RE the DROs, Particularly the X readout goes to 0. The Impact is when the code finishes, or is stopped, I try to send the gantry back to my soft set Home, it returns to the original Y and Z position, but soft home value for X has reset to the last G code position. That may be a clue that Mach3 is loosing the original X value somewhere.
Swapping the connections for the X motor and the Y motor on the controller resulted in the Y axis not moving in a -Y position, so I feel that eliminates a stepper fault.
The direction of the gantry and the DROs match, a movement in the defined -x,, -y and -z direction is reflected in the DROs by a declining number in the read out.
Hope that helps.
I appreciate conversing with a fine Scot. My ancestors hail from just outside Edinburgh.