I have no reply for you. But I have having huge issues with error messages with my students for all content. Canvas has no idea. Hope you find a solution.
I, too, do not have an answer for you...but I am hoping that @ffdixon might be able to chime in on this one...as he has been my "go to" for all things BigBlueButton. Hopefully he will be able to help address this issue with you. Thanks...take care...good luck!
I am the product manager for BigBlueButton. While I work at Blindside Networks, the company that provides hosting for Canvas Conferences to Instructure, and can't speak on behalf of Instructure, I can respond to your question.
We had made some recent improvements to students reconnecting and they shouldn't see the 401 error again UNLESS they have been removed from the session by an instructor who checked 'Prevent this user from rejoining the session'.