Excessive NSE flood caused by Manage Delivery Policy Detection Checks. The server is busy and the queue is backed up.
This error was also seen due to queue backup:
Fail to handle action[action=60c00ef0-9dd9-4f52-bcf8-e4116a4470be, id=54c13874-d8c0-43e5-80e0-46c6afeeb109, plugin=00000000-0000-0000-0000-000000000000, data=Symantec.WebSockets.AgentSocketStream, params=6] from agent[agentGuid=00000000-0000-0000-0000-000000000000, auth=False, connId=162114dc-ce2d-4daa-96b9-55273284e694, addr=xx.xx.xx.xx:65391, state=Opened]
System.AggregateException: One or more errors occurred. ---> Altiris.NS.Exceptions.NSComException: Agent connection is not authenticated
This is a known issue.
This issue is addressed in the Symantec Management Agent (SMA) cumulative fix for 8.5 GA. Reference ITMS 8.5 POST-GA Cumulative Fixes.