User is getting disconnected
See minimum bandwidth requirements for BigBlueButton.
If a user’s connection is not sufficient for the BigBlueButton session, the client may take a long time to load or, after a period of time, disconnect (it may look like to users they got kicked out).
The biggest use of bandwidth is webcams. If a session is sharing lots of a webcams, a user can elect to turn off the webcams on their client to (significantly) reduce the bandwidth requirements.
To turn off webcams, click the Settings menu