Outlook Client - Delete other users Appointment in Outlook doesn't delete in CRM

Hi All,

Having an issue using Outlook Client that happens to some users.

Our users manage other users' calendar in Outlook. They create, move and delete appointments. For some users, this works fine and all changes sync into CRM.

However, for some users, they can create and move appointments, while deleting appointments doesn't sync into CRM.

CRM Version: CRM Online (Dynamics 365)

Outlook Version: 2016

Have checked the security roles (even happens to system admin users)

All Mailbox settings are same

All Calendar Permission were checked

Any idea of potential causes?

Kind Regards,

Steven