I need advice. My Feeler VMC almost always make a noisy sound when I "zero return" the machine. Does anyone know where this sound might be coming from? Last month, I have asked cnc technician to replace the X and Y ball screw support bearing, but this crackling sound reappear. After the "zero return", the sound will disappear. Is there anyway to distinguish faulty support bearing or faulty linear ball screw? Thank you in advance.