those files may be a little bit older than when we discovered the suffix part of dfu-util..
maybe @BDub or @Dave could chime in as where to find the files that the CLI links to to check they have the suffix added?
command would be
dfu-suffix -c filename.bin //check if there is a suffix already
dfu-suffix -v 1d50 -p 607f -a filename.bin //add the core suffix
you can see the old thread here