So, I've finally gotten to step 6 in the printer commisioning chapter of the manual. I've loosened the z-axis motor, and I'm trying to lower the bed all the way using the motion controls (1mm, z axis, under the preparation menu). The firmware lets me turn the knob until the screen says 300mm (i forget if it's plus or minus), but won't let me lower the bed any further. At this point, the bed is only about halfway down to the bottom.. What gives? I have the new lead screws with the increased lead, and I've turned z-steps/mm down to 400, as per the manual. Any clues?