Been following this thread for a while now.
The G code for cutting a test circle is very straight forward:
G90 'Set the machine in absolute mode
G0X2.0Y0.0Z.1 'Rapid to .1 above material Z zero should have been set to surface XY zero should be center of material
G1Z-.1F30.0 'Plunge cut in Z to .1 depth
G3 X0Y0I-2.0J0.0 'Cut a circle 4 inches in diameter, center is located -2 from cutter location. Circle will be less than 4 inches.
G0Z.5 'Rapid up out of material
Ok, now for the dirt. Contrary to beliefs held by many cnc users. . . .cnc machines do not and cannot cut a true circle. The software breaks down a circular command into a series of very small steps. I will not bore everyone with the gory details but suffice it to say the control is optimized to handle the circular command. Attempting the same thing by programming a series of tiny steps will generally result in the motion buffer being emptied and then the machine goes into the herky jerky fits.
All that said, switching the control software was more than likely an attempt to to alter the circle algorithm. Probably not a good move but the easiest one to try first. They may now be suspecting that the pitch of the lead screw (if it has one on that axis) or the gear/rack pitch was goofed up. So that would be the next thing to attempt fixing.
Most of us check for motion accuracy by cutting a circle or square then getting out the dial calipers for a look see. But that is really measuring the result of cutting, not true machine motion. It includes all the mechanical slop and tool flex. To measure actual motion it is best to use a dial indicator with 1 or 2 inches of travel to see how each axis actually performs.
Sorry to see you are having these issues, but from what I have seen the company stands behind its products.
Low Profile CNC Router Vise