The appointment synch from Outlook to Dynamics 365 for sales/CRM has had functionality change. When appointments are created in Outlook and synched to CRM via synch filters, then the users decide they no longer want to synch appointments and turn the filter off, it cancels all future appointments in Outlook. When the filter is turned back on, the appointments flow back down to Outlook and get sent out from Outlook again.

Users should be able to decide they want to turn off the active appointment synch in the filters and NOT have Outlook appointments cancelled.