You uploaded some D3 raw files for exactly a year ago, and mentioned banding in them. I had no idea of the source of the banding. Now, by chance I found raw files of a few camera copies (D3 and D700) exhibiting a special kind of banding, which seems to be explicable (though not excusable).
Do you still own that camera? Have you observed the banding in other shots with low ISO, in smooth, otherwise clean areas?
The banding I encountered is always vertical, always with 12 pixels repetition. This is caused obviously by the readout electronics (12 channel readout).
Here is an example for the appearance of that banding: