So I think it's fixed.

There's no way to tell until new persons are added to group (apart from doing so just for the test).

Indeed the script will not be able to find out the data he got on file is not already up to date (otherwise the script would take hours each time).

Installation that have found this problem should run.

You may have to clean up all registered keyrings by running
rm -f `find /home -name "ascii-public-key"`
assuming that your users account are in /home.

Actually, the following should take care of such cases. But the bug is probably lying on this area, since clearly the problem occurs when a user join a group while he was already member of other groups and had already a registered key.

# Update of group keyrings
if ($gpg_group_keyring) {
foreach my $thisgroup (@{$db_user_group{$user}}) {

# Add the group to the list of update candidate, unless
# already there, if there were changes
if ($keys_differs) {
$gpg_keyrings_to_rebuild{$thisgroup} = 1
unless $gpg_keyrings_to_rebuild{$thisgroup};
}

# Store the key content if it is something worth being
# registered, in any cases (other users can cause the
# update to be necessary, so it's irrelevant whether this
# peculiar user needed the update)
if ($gpg_keys and $gpg_keys ne "NULL" ) {
push(@{$group_gpg_keyring{$thisgroup}}, $gpg_keys);
}
}
}