I was getting ready to start cutting when the spindle just stopped and it displayed Er 4, I try to find tutorial in youtube, this is the link: https://www.youtube.com/watch?v=psDq0weqs7Y and I try to set up like that. The the Er. 04 is gone. But when i try to rotate the panel potentiometer the frequency shows 10Hz the spindle does not move, until I set 47 Hz the spindle is moves. and the rotation is different, it is less noisy but I feel there is something wrong. Do you have any idea?