The workaround to the bad Samba DC startup, is edit/fixing krb5.conf under the nsdc chroot. Just run this command:
cp -vfp /var/lib/machines/nsdc/var/lib/samba/private/krb5.conf /var/lib/machines/nsdc/etc/krb5.conf
Then stop and start the samba DC process
systemctl -M nsdc stop samba
systemctl -M nsdc start samba
Now I must investigate why the nsdc container wants to download from 7.5 repositories 