Bucking the statement about people without D750 not having a right to post on this subject, I am going to post again, on this subject.
I have seen all the pictures that have been taken with said camera in said lighting conditions and agree that most of the pictures would have been a bit naff anyway because of the poor lighting, however I am beginning to wonder about what the symptoms of the fault actually are.
The thread talks about a dark band at the top of the frame, but this is not a dark band; on all the pictures it's a normally exposed band with the dividing line being a delineation between a correct exposure at the top and one suffering from flare underneath.
I offer this suggestion: That if the same photographs were taken with a camera that doesn't show this 'fault' then the flare would actually go all the way to the top of the frame and although the picture would be consistent across the whole frame, it would also suffer from flare across the whole frame and as such is just a photograph that shouldn't be taken without serious lens shading.