Suggestions for changing or checking settings have been made but this system has operated flawlessly for over a year with SketchUp as the CAD, SheetCam as the CAM, Mach as the operator, a Bob Campbell Designs breakout board as a liaison between an old PC and three Gecko 201s. The first sign of trouble presented while my Bosch 2-1/4 HP router, cutting through machinable wax, began a quick succession of jolts about 1/4" in length from Xnorth to Xsouth and back. No X movement was on the script at the time. The Y motion which was appropriate continued smoothly. Along with the jerky X motion was a grinding noise similar to that noise which occurs when steppers are trying to overcome an immovable object accidentally left in their path. The work piece was ruined and an emergency switch was slammed. Upon manual jogging, the X stepper would respond appropriately or the router would go in the same direction whether the Xnorth or Xsouth key was depressed. On some occasions the router would not move at all but a weak hum would emanate from the X motor. It was suggested by the forum that the Gecko could be removed and sent away for analysis. While proceeding to remove it, I discovered some less-than-tight wires on the Gecko bus boards. They were tightened and the code was run again. It appeared that all was well so I posted that the problem had been resolved. I was wrong. The grinding noise was gone and the left to right shuttering had ceased but a more subtle manifestation of the problem appeared. The wax project piece was now deformed by some errant tool paths that looked for all the world as though the wrong code had been loaded. But it had not. Marriss's last suggestion was that the breakout board might be the culprit. Not buying that for a second I put my Z Gecko in place of the X and vice versa. (No easy task in the tight quarters of my system) The Z was clearly not involved in the aforementioned behavior so this should confirm the X Gecko as the offending component. But it did not. The errant g-code continued. I re-ran the DXF through SheetCam. The image produced by that program appeared normal but I regenerated the g-code to rule that out. But my system, again, produced a deformed part. So here I am with most things ruled out. I should try another printer cable for the sake of completion but the breakout board seems the most likely cause at this time. Any input will be appreciated while I correspond with BCDesigns.