I had a few issues where this happened. Check your connections for the stepper motors. Pull them apart to see if it might be arcing. If they work free that will happen. I use a zip tie on mine now.
Static could be an issue also. This is what I did to help with that issue.
Grounding your Shapeoko - CNC Machines / Shapeoko - Carbide 3D Community Site
Good luck. Let us know