Since the files are owned by the users and root is simply the one
doing the backups, it is unclear why you are using sudo for the
users to see the files in restorals.  In any case, be aware that
sudo is similar to but not exactly the same as performing an
operation via 'su', as those of us using sudo for root operations
quickly learn when filesize limits cannot be had the same as when
doing 'su' or a root login.  Pick one of those problem usernames
and try an 'su' as compared with 'sudo' results.  You may have
some problem beyond that, but be aware of sudo limitations.
   Richard Sims, BU