synchronisation outlook Office365 calendar

I synchonised my Office365 calendar to week plan. It synced all my recurring appointments in outlook just fine. However, some of those recurring appointments i have removed from the outlook calendar just for next week. This does not get synchronised to Weekplan, they won't be removed/ deleted. I tried to delete them manually in the Planner view and that worked. Switched to the Weekplan calendar view and noticed they were still there. Switched back again to the planner view and they had returned. How can i remove these permanently just for this one occurence?