when I jog my x axis away from the stepper, everything works and sounds fine, but when I try moving the table back towards the side I mounted the stepper on, it sounds very rough, and sometimes stalls the stepper, this happens at any speed, and it doesn't seem to matter if I support the far end of the shaft (1/2" acme lead screw, 40" span) or just leave the end free, how could I go about fixing this?