Thanks JazzCNC for the response.

All of the axes are properly tuned and will move at rapid speeds consistently. This is an intermittent issue. Studying through the problem, I realized that when the machine is REF HOMED for all axes, the first axis to move is the Z followed by the Y and X is last or the third to move only it doesn't. When the Z decent issue occurs during the calibration code, the X & Y have all ready moved together and the Z is the third to move to make a measurement. Unfortunately, the issue is not consistent for a better diagnosis. The more that I ponder the issue, I'm inclined to believe that the issue is some sort of buffering issue within the communications between Mach3 and the MotionControllers via the ESS. The only configuration item that I have identified associate with buffering is around the Kernel Speed which is currently set at the lowest frequency for the max buffer size. But, that doesn't seem logical as the REF HOME process is moving one axis at a time, while the calibration code moves X & Y together and Z separately, which implies there is a counting issue within some piece of the communication process that isn't being managed properly.

I'll try to do some more investigating and post any findings that might pin point the issue.