We have installed Zimbra for one of our customers and they keep having a strange phenomenon with shared contact lists:

If user A shares a contact list to a group of users G they will all be able to see the contacts and everything ist fine ... until user A adds new entries to the contact list he shared.

All users in G will still see the old version of the list, without the newly added entries until they explicitly remove their shared version of the list and re-add it.

How can I change this behaviour so that all updates will be seen by all users who share a contact list?