I created two prints successfully with no problems but there was a slight screeching noise whenever the z-axis would move. After the second print was finished the bed moved down to the bottom but then starting to make a loud grinding and vibration sound. The only way I could stop this was to turn the printer off. I then tried to raise the z-axis manually through the control pad and by physically moving the rod, but neither of them worked. Any suggestions on how I can fix this?