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.
North America
Europe, Middle East and Africa
Asia Pacific