Using older versions of Outlook for Mac for personal email and calendar
I am also having the same issue. Our weekly standup was cancelled. I do not see the event in the MS Outlook calendar, but it is still visible on the mac native calendar. Switching to manual updates and pressing CMD +R to refresh does not remove that event from the calendar.
For me, it seems that this bug occurs to modified events. New events appear, but if the location or time is modified, or it is canceled, those changes don't get updated on the mac calendar.