I'm starting to think that your problem might be related to the UID/GID being different on your machines.
A user on this site explains the following:
You don't have the usernames in /etc/passwd on the new server and
that's why the owner/group names are not seen on the files you copied
Just copy over the appropriate entries in /etc/passwd, /etc/shadow,
and /etc/group from the old server to the new one and that should be
Does that make sense? In the comments I mentioned using the "stat" command on certain files/folders both on the client and server. Part of the output of stat will display the UID and GID. This may help in determining differences between the client and server.
I see that you have "firstname.lastname@example.org", but go ahead and make sure to add the "--super" option to your command.
rsync -x -r -t -v -o "nobody" -g "nogroup" --super --progress --delete -u --partial -s -e ssh /home/john/Calibre\ Library email@example.com:/media/Boo
Linux man page:
This option causes rsync to set the owner of the destination file to be the same as the source file, but only if the
receiving rsync is being run as the super-user (see also the --super
and --fake-super options). Without this option, the owner of new
and/or transferred files are set to the invoking user on the receiving