Are these errors still being experienced by users on Tableau Server? What version of Tableau Server is in use?
This is a pretty generic error and we would need a deeper investigation to understand the issue.
I also found this article that might be able to assist with the error: https://kb.tableau.com/articles/issue/error-opening-view-session-ended-by-server
I would also be interested for the error displayed in the logs if it could be provided.
Hope this helps!