I'm using Outlook for OS X 15.8. A couple of weeks ago I imported an ICS file into my normal calendar and then tried to delete the entries, because I wanted to move them to a different calendar. After that, one of the entries has started duplicating itself, so that there are now nearly 1,800 duplications of the same recurring appointment. When I run the desktop client, it crashes if I try to open the Calendar, or an e-mail containing a meeting invitation. I can open the calendar via OWA, however, even if I delete a few of the duplicated entries in the web view, they appear to return, so the number never significantly decreases.
Some of the suggestions I've read for similar problems appear to assume Windows clients, rather than OS X.
Is there anything I can do at my end, rather than the Office 365 end? I don't currently have access to a Windows desktop.