The above error usually means that you are trying to write to a connection when the other end has already closed it. In this case it seems to be an issue with the underlying source. It would be great if you could check any issues with connectivity at your end as well (i.e., it could be related to a firewall or load balancer, you should check with your network administrator).
The logcontroller stored procedure is useful for getting more information. For more details, you can refer to the [Using logcontroller and useful log categories](https://community.denodo.com/kb/en/view/document/Using%20logcontroller%20and%20useful%20log%20categories) Knowledge Base article.
If you still need help and if you are a valid Support User, you may open a Support Case at the Denodo Support Site and the Support Team will help you.
Hope this helps!