MSExchange Mid-Tier Storage Event:3019 on Exchange 2013

I am having the Event 3019 on Exchange 2013 with Source "MSExchange Mid-Tier Storage" and have not been able to find any reference on the net for this. No other failures are reported. The server is serving clients normally.

Version: Exchange 2013 CU19
Build Number: 15.00.1365.001
Installed on Windows Server 2012R2 64-bit
The server has 2 mailbox databases on the same machine, each one on different hard disk.

Here is the complete message:

Synchronization of discovery and hold configuration to Microsoft Exchange online failed because of error:
Microsoft.Exchange.Data.DataSourceOperationException: The request failed. The remote server returned an error: (401) Unauthorized. ---> Microsoft.Exchange.WebServices.Data.ServiceRequestException: The request failed. The remote server returned an error: (401) Unauthorized. ---> System.Net.WebException: The remote server returned an error: (401) Unauthorized.
   at System.Net.HttpWebRequest.GetResponse()
   at Microsoft.Exchange.Data.Storage.Management.EwsHttpWebRequestEx.Microsoft.Exchange.WebServices.Data.IEwsHttpWebRequest.GetResponse()
   at Microsoft.Exchange.WebServices.Data.ServiceRequestBase.GetEwsHttpWebResponse(IEwsHttpWebRequest request)
   --- End of inner exception stack trace ---
   at Microsoft.Exchange.WebServices.Data.ServiceRequestBase.GetEwsHttpWebResponse(IEwsHttpWebRequest request)
   at Microsoft.Exchange.WebServices.Data.ServiceRequestBase.ValidateAndEmitRequest(IEwsHttpWebRequest& request)
   at Microsoft.Exchange.WebServices.Data.MultiResponseServiceRequest`1.Execute()
   at Microsoft.Exchange.WebServices.Data.ExchangeService.FindFolders(FolderId parentFolderId, SearchFilter searchFilter, FolderView view)
   at Microsoft.Exchange.Data.Storage.Management.EwsStoreDataProvider.InvokeServiceCall[T](Func`1 callback)
   --- End of inner exception stack trace ---
   at Microsoft.Exchange.Data.Storage.Management.EwsStoreDataProvider.InvokeServiceCall[T](Func`1 callback)
   at Microsoft.Exchange.Data.Storage.Management.EwsStoreDataProvider.GetOrCreateFolderCore(String folderName, FolderId parentFolder, Func`1 creator)
   at Microsoft.Exchange.Data.Storage.Infoworker.MailboxSearch.DiscoverySearchDataProvider.GetDefaultFolder()
   at Microsoft.Exchange.Data.Storage.Management.EwsStoreDataProvider.get_DefaultFolder()
   at Microsoft.Exchange.Data.Storage.Management.EwsStoreDataProvider.<>c__DisplayClass1b`1.<InternalFindPaged>b__13()
   at Microsoft.Exchange.Data.Storage.Management.EwsStoreDataProvider.InvokeServiceCall[T](Func`1 callback)
   at Microsoft.Exchange.Data.Storage.Management.EwsStoreDataProvider.<InternalFindPaged>d__21`1.MoveNext()
   at Microsoft.Exchange.MailboxAssistants.Assistants.ELC.DiscoveryHoldSynchronizer.GetDiscoveryHolds(DiscoverySearchDataProvider dataProvider, Dictionary`2 discoveryHolds)
   at Microsoft.Exchange.MailboxAssistants.Assistants.ELC.DiscoveryHoldSynchronizer.Synchronize(Object argument)
   at System.Threading.Tasks.Task.Execute()

What is the CU version of your exchange 2013? Does this issue affect end users?

I have done some research on these error messages, this problem can occur when NetBIOS over TCP/IP (NetBT) tries to query a loopback adaptor as a destination device to determine network speed. For more details: Event ID - 3019

If there is nothing wrong with end users, you could ignore this event.