Intermittent stepper problem

[HomerSimpson]

I am building my second CNC router and am re-using my Gecko G540, steppers, and cables from my first machine, where they worked with no problems. I am using Mach3 with an Xbox360 controller to manually position the router. It uses a USB port and interfaces with a plugin that someone wrote for it in Mach.

One of my axis just starts taking off without any input from me. It is not a constant velocity and may or may not stop on its own. I swap cables on the G540 and the problem follows the G540, not the stepper/cable assy.

Does anyone have any ideas on what the root cause might be? I have searched various forums, google, etc. and either I'm not using the right search terms or no one else has seen this.

[CNC Lurker]

Are you using the default screenset that came with Mach or a different one? Your problem sounds odd because it's not a constant velocity and goes without input, but I would move the joystick and it would move a distance and then it would stop.

I have the Mach 2010 screenset and it turned out I didn't know I was using the step setting in jog.

I don't remember if there is a home option on that XBox 360 controller plugin, but I wonder if one of the buttons could be set for homing.

[HomerSimpson]

I'm such a Mach3 rookie. How do you change the screensets and then how do I change the step setting for jog?

I do think it is related to the controller. Last night, I let the machine sit for probably an hour with the 360 controller unplugged, but with current going to the motors and Mach3 running and it didn't start moving on its own at all. Thanks.