Continuously receive multiple calendar meeting responses from the same person

We have recently noticed that some of our clients continuously receive multiple calendar meeting/invite responses from the same person. 

Microsoft is investigating an issue which causes duplicate meeting responses to be sent from iOS 9.x devices using the built-in mail and calendaring application.  If a calendar event is created and a recipient responds to the event using an iPhone with iOS 9.x, the creator of the event may start receiving multiple meeting responses from a recipient.  The duplicate responses do not always come from the person who responded to the calendar invitation on their iPhone. They can come from anyone who was invited to the event.  Currently, it is unclear if this issue will require a fix from Apple or Microsoft.

To resolve the issue, we had to run them through these steps:

1. Open Settings
2. Select Mail, Contacts, Calendars
3. Select your Exchange account
4. Tap the switch next to Calendars to disconnect the calendar
5. Tap the Delete from My iPhone option
6. Tap the switch next to Calendars to add the calendar back