This is a follow up issue from the darktable issue (darktable-org/darktable#9447).

tldr of 9447:

• Silverfast (filmscanner) may produce DNG files with additional exif data (IFD1 + PreviewTiff) which causes rawspeed to report the image as corrupt.
• sample images found here

First thought, as shared within the 9447, was that because of the IFD1 Block rawspeed may fail. So I tried to remove it.
I ran exiftool -all= <file> and magically rawspeed (accessed via darktable) could read the image and all went well. Hurray!
Now I tried to find out whats different within the files.

I made a diff of the exiftool -v output (see attached) and the IFD1 and PreviewTiff Blocks are still present, but what was removed was:

• IFD0:ApplicationNotes
• IFD0:ExifOffset

I tried removing those by hand. IFD0:ApplicationNotes could be removed, but didn't change anything. The image was then still reported as corrupt.
IFD0:ExifOffset could not be removed by hand with exiftool (it says "not writeable"). Does anyone has a tip how to remove it?

But as ExifOffset remains, I guess its whats causing the error and I guess its the content of the MakerNoteUnknownBinary.

Any Ideas how to check that?

Here are the exiftool -v outputs and diffs.
exif_meta_vs_no_meta_diff.log
exif_w_meta.log
exif_wo_app_note.log
exif_wo_meta.log