After having many attempts to rectify the below issue:
One user (Sue) is having some issues with two shared calendars which, reside on separate shared mailboxes. The issue resides solely in the Outlook Software, OWA does not have this issue and making changes here is visible to everyone. She has problems where she can see the Calendars, even add/edit/remove updates but she doesn't see any of events that are already in there and no one can see her updates, if you restart Outlook they have gone. I've done the basics including removing her personal Calendars to re-profiling in on different user accounts, the issue follows Outlook Software.
I suspect it's something to do with ActiveSync Cache, so drastic as it may seem, what I was thinking to troubleshoot next is to backup Sue's mailbox, create a fresh mailbox (this is where my knowledge gap lies) share the calendars with her again, make sure this can be accessed and then restore the mail,
I'm just not 100% on how to do this without causing the disaster of a broken inaccessible mailbox,
Any advice on methods?