I have tightened all the bolts on mine so all the bearings touch and it made it worse. I ran it real tight for a few hours hoping to wear the zinc coating off the rails. It did wear a bunch off but did not improve smoothness of the movement.
I am almost 100% convinced that it has to do with the texture, length and flex of the emt rails at that length. I discovered yesterday that my local hardware store has 1″ x 72 stainless closet rods. I am going to start reprinting the 1″ version. Those closet rods and quite noticeable stronger then the emt.
@vicious1 can I leave the 3/4″ legs in place? Will the 1″ corner pieces sit on top of the lock corner?