Solution: Shifting/banding on y-axis during tall prints
Recently I had a problem with tall prints where shifts in layers (only in the y-axis direction) got progressively worse the higher the print went. I searched all around and couldn't find anything, so this is for future people in need.
Turns out the base platform did not have all four feet planted horizontally and when the bed moved it caused the metal frame to vibrate back and forth (in the y-direction!). In the end I straightened the base as best as I could, however some feet were still slightly off the ground. To compensate for the gaps I applied small amounts of Blu-tack to the feet which effectively eliminated the vibrations and this resulted in a perfect print 😀 .
To find lifted corners, repeatedly and firmly tap each corner of the base and see how much the metal frame vibrates and the sound of the corner hitting the ground should also be eminent.
Hope this helps!