Nothing concrete to add, Gerry, but it reminds me of when the D200 came out - my first digi body - and the 'small' matter of banding raised its head. Seemed to be the case that it was only happening on some bodies, and not across the board, but tough if you were unlucky.
Perhaps you have been unfortunate, but let's hope there's an easy, downloadable fix! Maybe you should have kept that M6... ? ;-)
Best wishes -