I had a failed print last night. At first it appeared as though the hobbed bolt had stripped out on the filament (common problem for me with Inova 1800), but the z axis had stopped moving up and had then caused the filament to strip due to the excessive pressure. Now when I power up and try to move the z axis, it hums but doesn’t move. I first checked to see if the left and right had become out of alignment, but they were good. The screws move freely. Can anyone give me a good starting point for troubleshooting?