Hi Rahul,
version 1011.0.12 has a bug with websocket connections. If you would have searched for the invalid frame header message within this forum before posting this, this would have been the first result: Local cumulocity web app dev server is not sending realtime notification - #2 by Tristan_Bastian
This is e.g. also covered as part of the release notes: Applications - Cumulocity IoT Guides
Regards,
Tristan