Z banding at very specific heights  

Z banding at very specific heights

I have been printing some cylindrical items (plant pots) and experiencing Z banding that occurs only at very specific heights.

For example: at the layer where the solid cylinder becomes a hollow cylinder, there is very visible banding.

Or, if there are multiple parts, the layer at which one part ends has banding on the part that still has more to print.

I have attached some pictures that should make it quite clear. And to be clear, the models/sliced files don't have anything weird going on at these spots.

Here you can see very clearly the issue on the left. It occurs at the layer where the solid base stops and the hollow cylinder begins (last pic shows view from the top).

If you look closely, you can see if also where the part on the right ends, the left part has a bit of it, but not as severe.

The other part experiences the same issue:

Other that at those specific heights, the prints are incredibly smooth. Any ideas as to what could be causing this, and how to alleviate it?