Licensee reported getting this error on PS4 after losing internet connection or putting the console into rest mode. See linked UDN for callstack.
The NetConnection calls Close during its Tick, due to the connection timing out. Then from there, the NetConnection calls FlushNet, which triggers another error within HandleSocketSendResult, this time causing GEngine->BroadcastNetworkFailure to be called.
See comment with CL to reproduce the issue.
There's no existing public thread on this issue, so head over to AnswerHub just mention UE-115581 in the post.