Just got my R2 and the second setup step -- calibrating the Z axis via the Z Offset Wizard -- isn't working. The bed rises up to the extruded nozzle and keeps going. It makes a horrible grinding noise as the motor and screw keep turning, jamming the bed upwards into the extruder. It doesn't auto cutoff, as I assume it should. Then the extruded nozzle starts to move, scratching the bed. At this point I do a hard power shutoff to prevent the R2 damaging itself. I'm stumped. I assume it should stop just short of the extruder nozzle, and then have me fine tune the gap via the touchscreen. Where's the shutoff switch for the z axis? Couple of things: When the printer arrived, the four adjustment screws under the bed seemed loose -- one actually fell off. So I tightened them. But the bed is still too high and grinds into the extruder assembly. I also called tech support three times. But each time, their phone system somehow hung up on me! Very frustrating! Any advice?