Hello, I am new to 3d printing and got a preassembled RepRap i2 in the mail. The bolts attached to the motor that controls lifting the nozzle on the z-axis is loose. How can I adjust them? I provided an image of the bolt I am referring to. When I calibrate the the printer it gets stuck and cant move down. Thank you.by JeronBraxton - Prusa i3 and variants