Hi Uli, thank you again for your reply!
I have absolutely no problem to view the NEF-files in the finder. They are shown pretty good there but as explained not in DRS.
I've created an archive with files I can and I can not open.
The files 0233 (Z6), 0306 (Z6), 0309 (D5100) can be added to the media pool in DRS and are shown. But if I begin to edit one of the files 0233 or 0306 the "viewer" turns black and nothing is shown again. I am only able to show the files without making changes to them.
The files 0418 (Z6), 0685 (Z6) are directly shown as "media offline".
I don't understand the differences between 0233, 0306, 0418, 0685 and 0309 yet.
The data is temporarily available via this
https://drive.google.com/file/d/1TJ6IpK ... sp=sharing