Outlook Calendar Appointments - Duplicating Attachments

Getting a screen like this on your Outlook Calendar Invites?

Currently, this is a random issue Microsoft is working on.
They have a temporary work-around, however it is not permanent and the issue will come back.
Once we have a full resolution for this issue, we will inform you here...

Workaround 1:

To mitigate the issue, you can use the Clear Offline Items for your calendar. This step clears the calendar items in the Outlook store (OST) on your local machine.   

To clear offline Calendar items, follow these steps: 

1. Open the Calendar pane in Outlook, and right-click the Calendar folder.

2. Select Properties.

3. On the General tab, select Clear Offline Items.

4. Select OK.

After you clear offline items, Outlook will re-sync the calendar and repopulate your calendar folder with the calendar items on the server.