That sounds like then with the change to MS Graph as per @Michal_Burger advised below should then hopefully resolve these issues you and others are experiencing in this thread.
For me personally using the latest V10.4.5326 PC or Mac i have no current AirSync issues with my own Live, Hotmail or Outlook accounts as far as Mail, Calendar, Contacts or Tasks go, so i suspect its possibly either eg: Microsoft Server issues randomly happening on some mirror servers around the globe, or some other external unknown factors causing these ongoing issues.