Mani, It is difficult to pinpoint the underlying problem but device logs will definitely help.. You'll need to enable logs for your mobile client using debugging options on Mobile build screen. You can either retrieve device logs onto server using Mobile->Offline landing page or see logs on Chrome/Safari by connecting your device to PC/Mac.
Like I said, go to Mobile->Offline landing page and locate Retrieve device logs tab. Specify the operator you use to login in offline applications. Login to offline app and reproduce the scenario and hit 'Retrieve device logs' on landing page. This will post relevant device logs to Pega log file on server.