I have delt with this problem since I first received my machine (used). I'm sick of it. After I complete a run with a mill, the z axis begins to rise and the spindle and coolant turns off as it is rising to the tool change position. Sometimes, during this process I hear a thump in the machine, then the spindle starts back down and will not stop until it crashes or I hit the estop. It happens somewhere after the tool has risen 2 inches and before it reaches tool change position and at random distance. It is not in my code as it does it with code generated from Mastercam, and Sprutcam. It does it very randomly and not always on the same program or the same tool change within the program. I have talked to Tormach about this and have reloaded mach and have switched the drives around and it continues to do this only on the z axis. anyone ever had to deal with this or know a fix?