hi Chandan,
 
OnRemoteHangUp is a first party call control, so it doesnot need any kind of monitoring or controlling of devices. Also irrespective of which protocol you are using, if the other end hangs up the call, remoteHangup event is invoked. If the remoteHangUp works for one device and doesnot work for the other device in that case i doubt may the call is not got disconnected properly. You might need to check the CUCM logs to confirm if the call is actually disconnected.
 
Thanks
Nabhonil

Hi Chandan,
 
What does the log say? Make the Application Server, Application manager and Application Environment as verbose. Reproduce the issue and send us the logs. Also if you can give the snapshot gif image for the remoteHangUp event it will be easier for me to debug it.
 
Thanks
Nabhonil