I recently had to replace my Mini and I’ve noticed some banding with my newer printer. I printed some test objects (9 square tubes located in 3 rows of 3 objects covering the entire buildplate) and saw the banding pretty clearly about every 2mm in the X direction (buildplate position did not seem to matter). I spent some time watching the screws spin and it looks like there is a little wobble in the right sided one, but is subtle and I didn’t have my close range glasses on and can’t say that for sure. Then I started fiddling with the right hand screw while futilely trying to see the set screws and figure out which hex tip to use without the right glasses. Anyway, in that process I rotated the right side screw by hand to get a view of the set screws (probably a half to 3/4 turn). After doing that, I became curious about what the print would look like if I did not turn the screw back to the original position. So I ran the same print again.
Interestingly, there was a big reduction in how pronounced the banding was. In the picture below, are two test pieces. Both come from the left front section of the buildplate, and both were printed with the same settings with same material (eSun ABS 0.25mm layer height), in both, the face shown is the face pointed toward the right side of the printer.
A: before rotating the right hand screw.
B: after rotating the right hand screw.