I got a Chinese CNC that I retrofitted with a G540. However, I cannot get the stepper motors to operate smoothly. I would appreciate any help offered. My guess is that it's a Mach3 software issue because I tried a 4th axis stepper motor from another machine and it does the exact same thing as these three stepper motors. Here's a link to a youtube video for it.

https://youtu.be/rOzktfUynF8

Thanks for the help.