The build instructions have you assembling the print bed platform while the printer is on its side. If you do that, the platform will likely be slightly higher on one side than the other. (mine was). When you level the bed, it will cause the bearings to bind. You need to set the printer up right, loosely attach the extrusions between the brackets, hold it down flat, such that the linear bearings press against the base, and then tighten the screws in a star alternating pattern starting with the outside four and than finishing with the inside four.