I had a problem with my Z travel on both platforms. I discovered that the bearings for the stepper motors and the metal "floor" that surrounds the bearings were not in good alignment with the holes through the rest of the structure. There was severe binding once the assembly of that section was placed. A good portion of the mechanism had to be removed in order for me to slightly enlarge the pass-through holes and to push on the bearing floor (stepper motor assembly) in order to remove the binding. I have not yet tested my modification since the re-assembly, however, so I cannot say how successful it was. There is enough freedom of movement that I can rotate the screws when previously I was unable. The manual does indicate careful measurement is needed, but a sharper note regarding clearance and alignment would have been useful.