Two receptionists both have access to a user calendar created solely for booking out time slots in a meeting room.
Both have been assigned full access permissions over the mailbox through Exchange.
Both have been assigned Owner permissions within their Outlook profiles over the calendar for the mailbox.
Was working as you would would expect. Both could see existing appointments and could add new ones.
This has now stopped working for one of the receptionists. She is still able to add appointments but they don't show up when viewing the calendar from her Outlook. However, they show up as normal in the second receptionist's Outlook.
I have uninstalled Outlook 2010, and given her Outlook 2013. This resolved the issue for a day or two before the problem resurfaced.