We are in job of repairing cnc electronic parts one of my friend called me to look at one of his friends cnc it was cincinnati milacron arrow 750 the problem was the drift on the a axis. we tried all the drives on a working cnc they worked pretty well changed the cable of the axis motor we tried axis motor at another axis it worked we changed the place of the axis drives we tried to fix it with the zero pot on the driver. Still when the machine powered the a axis motor starts to turn without control and on the screen we see the error a axis limit exceeded. what can be the problem?