distorted dng files

[Alexander Linkenbach]

Hi
I recently scanned in some negatives as dng files and some of them (not all)
not have got a strange appearance: kind of twisted a bit counter-clockwise
with the top right part in the bottom left instead. It did not happen during
scanning, firstly because I checked most and secondly the imbedded thumbnail is
ok. This has only happened to some files in landscape, but to none in portrait
orientation.
Anybody ever had that problem and maybe know how to fix it?
Alex