I've been pixel peeping the same images I have uploaded in this post (it is still available for download) and found some artiafcts. Note the banding in the shadow under the ski tip:
Click the image to view at 100%.
I've been dragging a lot of sliders back and forth and found that the Shadow seem to be the root cause. Though, resampling caused by Lens Corrections seems to make matters worse. Also, high Noise Reduction seems to exaggerate the issue, wiping the noise that naturally interferes with the banding artifacts.
I suspect this has nothing to do with the sliders, just that some bring it out more.
You might post the camera model. Some of these were reported previously and Eric was working on those.
It's a Nikon D80.
I have tried pulling those shadows with just the curves instead of Shadows and I could not get any artifacts.
EDIT: The raw upload I have mentioned in the OP is a reduced resolution dng, so it might not be of any use.