Strange Z-banding/ribbing

I've suddenly started experiencing a strange Z-banding issue. It appears that roughly every 10mm in height a few layers will shift very slightly and then go back to normal right after. This wouldn't be super strange on its own, but what makes it really weird is that the print immediately before this one didn't do that. You can see both prints together with my sausage fingers for scale in one image, and a better view of the shifting I'm describing in the other.

Check if the z-screw is bent, or if your z-axis in general is at all loose.

So it is as if periodically a layer or two gets shunted towards X or Y a bit before returning
back to the original position?
I was getting rhythmic shifts myself. Ended up slowing the Y speed and tightening the heck out
of the Y belt

I just finished replacing several parts of my printer and will update with results after my next large print. Even though I don't understand it, I think epicepee may have been right.

Check you z steps. It may be that you are close but it is "correcting" as it goes up. also looks like you are over extruding.