Modifying the database inside of a backup to remove a duplicate key tag so that it doesn't fail when restoring

I think it has to do with the file paths. Have a look at

Hmm. That might not be the issue. I mostly don’t trust 7zip to create a compatible tar file, but that may be irrational.

  -h, --dereference
              Follow symlinks; archive and dump the files they point to.

The answer might be in the file above. Actually, it’s probably in another file in the same directory.