If you have a Resource account where delegates using it are not seeing changes made by other delegates (this can be random behaviour or constant). For instance a delegate opens, moves or deletes an email, or makes changes to a shared folder and one or more of the other delegates does not see this change.
Then ALL of the delegates with access to the Resource account need to do the following to resolve the issue.
Accessing Resources in online mode rather than cached
1. From Outlook 2010 client.
3. Highlight your account and click Change.
4. Click on More Settings
5. (Unlike the screenshot below you will have resource(s) listed under 'open these additional mailboxes'.) Un-tick the Download shared folders and click OK.
6. Click OK.
7. Click Next.
8. Click Finish.
9. Click Close.
10. Now you will need to restart the Outlook client.