iPhone Calendar not syncing with Exchange when calendar conflict

Hi all,

I am using iPhone 6 plus + iOS 9.3.1. My iPhone Calendar sync with Exchange Server 2010. Recently, I discover that two conflicted appointments cannot sync with Exchange Server at same time. Only one appointment can sync with Exchange Server. Information list below:

Appointment 1 : test 01

Start Date : 2016-05-13 8:30am

End Date : 2016-05-13 9:30am

Appointment 2 : test 02

Start Date : 2016-05-13 8:30am

End Date : 2016-05-15 10:30am

Only appointment 1 can sync with Exchange Calendar. However, I changed the appointment 2 start time from 8:30am to 09:31am, appointment 2 can be synced with Exchange Server. Two appointments can be viewed on OWA or Outlook.

I tried to create same two conflicted appointments on Android device. Two appointments can sync with Exchange Server.

I remembered that I could sync two conflicted appointments with Exchange Server Calendar before (iOS 9.2 or before). I want to know that if iOS 9.3.1 have updated this conflicted appointment issue?

Thanks.