I am not able to reproduce your error. The 401 typically means unauthorized access but you have mentioned this looks to be an intermittent error. What I would suggest is to log the incoming web requests and analyze when this error occurs and then analyze the vdp.log and the catalina log file created on the day when the error occurred under <**Denodo_Home**>\resources\apache-tomcat\logs.
To log incoming requests, you can follow the steps mentioned in the following Knowledge Base article[ Logging incoming web requests](https://community.denodo.com/kb/en/view/document/Logging%20incoming%20web%20requests).
In case you need further assistance and if you have a valid Support Account then you can reach out to Denodo Support by raising a support case on [Denodo Support Site](https://support.denodo.com/MainPage.do) and the Support Team will assist you.
Hope this helps!