I borrowed another 1D2N from a friend to test for this shadow thing again yesterday. The shot was taken with iso 100 and the shadow effect was obvious in the pic. I guess it is pointless to go back to Canon with this thing though since 1D2N is discontinued, they might just want to sleep on it until it goes away.
Yes, I did. It did not help. Do not have no 1D2N no more.
I think it is most likely caused by in camera software, a firmware update might solve it. Since Canon did put a new CMOS and Image Engine in my 1D2N when they were trying to fix it but none helped.