My thought is that mine only got very tight when the ball screw was attached to bother fixed bearing. The outer bearing when It pops out you can see it's lifting up higher than the hole by about. 0.25 mm, you can get it back in the hole only by using the locking nut to pull it into places but then the ball screw is very tight in the bearing. Can't be rite forcing the bearing over the shaft into the hole, it's putting downwards force on the screw. Making it squeezes up on the bearing. Hope that makes sense. Lol