The subject is a bit of a rhetorical question... I just finished Step 4 from the Step by Step Assembly Process. I've noticed that there is binding on the left side as I move the assembly towards the rear. If I start with the assembly at the front of the printer and slide it back, the part labeled "Y-AXIS BACK (R)" in the "Y-AXIS REAR ASSEMBLY" image creeps back and forth on the bar, as if something is not square. By the time I get to the rear of the movement it is binding fairly tightly Back when I was getting started with the build (last June, in fact) I cracked that very piece and the fine folks at BigBox sent me a replacement. I wonder if the pair were supposed to be matched? Should I send the STLS for both parts off to Shapeways (or ...) and get a new pair made? Thanks, g.