Layers shifting equally in BOTH directions...Possible Z motor failure?

[175_Pilot]

So I have the oddest issue ive ran across thus far in my 3d printing days and hope that someone else has had this issue as well.

We've all seen a layer shift. One axis kicks over in one direction and continues printing thereby offsetting the whole print. Ive got a different problem entirely. My layers are shifting equally in both directions as you can see in the attached photos.

I have gone through and checked the steps/mm on each axis and even confirmed them all by resetting them. I have adjusted my motor drivers to the recommended settings for the drivers used - still no dice.

When looking closely, the "shifted" layers are actually appearing much more closely stacked together than my other layers - setting is currently at 0.2mm/layer, but these shifted regions look to be about 0.1mm/layer or less. This is cluing me into the fact my Z axis may be intermittently failing and as a result stacking a few layers before catching itself again. The odd thing with this issue is that it doesnt start until a good way into the print as you can see.

Photos in my drive as I realized that as a new member I cannot post photos yet.

3d print hub - Google Drive

Anyone have any clues? Thank you all a ton in advance!