I had a strange experience using BBB where we had two meeting rooms running concurrently from the same activity link. I had created the initial meeting room and one of the participants was then able to create another. All the other participants entered my room apart from one who ended up in the second room.
The activity is using Separate Group mode in the settings but there is only one group set up and all current participants have been added to it. I'm using MoodleCloud.
Any advice as to why this might have happened?