Hi! I'm getting consistent horizontal banding at a specific location in every print on my UM 2go, and suspect the problem may be with the bearings or z-nut (I cleaned and lubricated the z screw to no avail). But, I can't figure out how to remove the z cap? The assembly manual for UM2 shows z cap screws underneath the build plate, but I don't find these screws on the UM 2go. How do I remove the z cap? Grateful for any help, or pointer to an assembly manual for the UM 2go!