Symptoms

Users seem to be getting the following message occasionally whilst using SmartForms: ?The remote server returned an error (401) unauthorized? If you click "OK" and refresh the page the error goes away.
 

Diagnoses

From the SharePoint ULS log the following errors were noticed:

"Unexpected error occurred in method 'GetObject', usage 'Distributed Logon Token Cache'" followed by "The request timed out."

From researching this error, the following Blog posts were found:

https://newsignature.com/articles/distributed-cache-errors-in-sharepoint-2013/
https://blogs.msdn.microsoft.com/sambetts/2014/05/28/troubleshooting-appfabric-timeouts-on-sharepoint/

 

Resolution

Client was advised to review the articles to see if this could be the cause of the issue. Client responded that they fixed the errors in the Distributed Cache by applying latest AppFabric updates and that this resolved the issue.