Appointment Double ups in CRM 2013

Hi,

I have asked this question some time back but did not get a solution.(https://community.dynamics.com/crm/f/117/p/154352/359828.aspx?WT.mc_id=ForumAnswerReminder#359828).  My client is getting duplicate Appointments time to time when completing them. I was able to re-create this multiple times and it created duplicates when completing an  Appointment(just after saving )and when saving an Appointment multiple times. We installed the latest update Rollup(Update Rollup 2 for Microsoft Dynamics CRM 2013 Service Pack 1 - released in Feb 2015) but that did not fix the issue. Any help would be much appreciated.