Symptoms:
Outlook 2013 users will sometimes be able to use the scheduling assistant and other times they won't get any free busy information. When they can't get the free busy information they are also unable to set their out of office.
It will work one day (or week) and won't work the next. I think restarting Outlook can introduce the problem or resolve it. I guessing there is some way Outlook connects to the availability service on startup that determines if they will have the issue or not.
Answers to questions you may be thinking of:
OWA scheduling seems fine but it's not used enough to be meaningful.
It's not the patches mentioned in this artible http://helpdesk.missouristate.edu/news/two-microsoft-updates-cause-problems-with-outlook-2013. I installed KB2850061 to address this.
Outlook 2007 users don't have this problem. In the past though Outlook Anywhere 2007 users haven't been able to set their out of office but I don't know if this is still an issue.
I feel like I'm chasing a ghost on this one. Thankfully the users haven't been bugging me about it much. Thanks in advance.