Hey folks, need some help. I finished an overnight print and noticed at the top of my print a weird banding, but the print completed. When I tried to print something next and go through the nine-point calibration, the left side z rod made a buzzing noise and did not move. The right side of course does so I powered the printer off. I let the left stop float free to see if the z rod screw would turn but no, it just buzzes. Any idea? I can hand-turn it but cannot move it via software.