Intermittent stepper control problem with G540

[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 channel, 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.

[ger21]

If the DRO's in Mach3 are not changing while the axis is moving, then it's not coming from Mach3.

[HomerSimpson]

So I'm a novice and don't know what DRO stands for but if you mean the coordinates on the main page, then yes, they are changing.

[ger21]

Sounds like the XBox controller is causing it then.