Tell me about the issue and I’ll help you find the solution you need.
Calendar item body disappears in Outlook online mode in an Exchange Server 2013 environment
Content provided by Microsoft
Applies to: Exchange Server 2013 EnterpriseExchange Server 2013 Standard Edition
Assume that you compose or edit a Calendar item by using Outlook Web App or an Exchange ActiveSync device and then save the item. When you open the item in Microsoft Outlook 2013 or Outlook 2010 in online mode, the body of the item disappears.
This issue also occurs in Outlook Contacts and Notes.
This issue does not occur in Outlook Web App or Outlook in cached mode.
To resolve this issue, install the following cumulative update:
2961810 Cumulative Update 6 for Exchange Server 2013
This issue occurs because Outlook in online mode cannot convert the content from the body of Calendar items, Contacts, or Notes so that it displays correctly.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.