circles coming out distorted?

USB smoothstepper
C25 breakout board
gecko 201 stepper drivers
Smoothsteper board ver 1.2
plugin smoothstepper SmoothStepper_v17fe
12 vdc proxy sensors on X and Y as homing switches (opto relay board triggers signal)
machine is 3 axis mill running mach 3

After doing many upgrades including updated SS driver and plugin, new computer, touch screen monitor I'm having issues with files to cutting properly.

I've checked the calibration of the axis and they are spot on. The first thing I noticed that was peculiar was when I loaded the attached file and it appeared in the mach cut screen was that id was elongated and not a circle. I didn't pay that much attention at first and just figured it was because the new touch screen wasn't displaying properly and probably just needed a driver or maybe adjust the resolution.

However upon cutting the finished piece was in fact oval and not a circle as drawn in CAD.

Any Ideas? G code attached.

It's round in Mach3 here, and should be cutting round.

Machine flexing or loose coupling?

checked that. Actually found a few loose bolts but that wasn't the culprit.

This is happening even when cutting light cuts in soft plastic so as stout as this machine is there's no way it's flexing that much.

Steps/unit error? Not sure why it would not be round on the screen, unless your screen is some strange resolution.

checked calibration on the machine and the problem clearly is not mechanical. Yesterday I loaded Mach onto my laptop and the part cut fine. Switched out the computer running mach to another desktop running Win7 home premium.

Cut a 2x2 inch square and checked measurements all good. Next cut a 3 inch circle, came out perfect. So now I'm celebrating...... until I try another circle and this time the top half of the circle is a perfect arc but below the equator line I've got distortion on the screen and no doubt ably if I machine it.

Found a different Post processor will try loading that in to my cad program (BobCad 21) but I doubt it will make a difference.

My USB Smoothstepper is Ver 1.2 and is 10 years or so old. Any idea if the early one's were buggy?