Video Layout Not Changing As Participants Speak

Hi All,

I work down here in San Diego and our court system is transitioning to Microsoft Teams for remote hearings as the COVID-19 crisis continues. Generally, we're having reasonable success with occasional hiccups. Today we had an issue that was very problematic, hoping for some guidance:

There are approximately 50+ participants/attendees on during the course of the hearings. Most (I'd say 40+) were muted with cameras off throughout the hearings. Various attendees/participants (at least a dozen) reported the issue.

Issue:

Attendees and participants noticed that videos were not changing as expected on their 2x2 video grids (the 4 active videos shown on screen to everyone). People noted that one particular participant who was muted with his video off had his static image on screen (as if pinned, but all participants/attendees assured me that there was no pinning) throughout much of the hearings. This was true even when there were other participants/attendees speaking with their videos on and mics active but were not having their videos displayed on screen. Effectively this meant that we only had 3 videos actively transitioning to active participant/attendees and one static picture of someone from my office occupying one of the slots. 

Other Notes:

(1) The static image did not belong to someone within the host organization;

(2) Static participant never attempted to disconnect and rejoin the meeting;

(3) Reported by at least 12 people, all working remotely from different locations

Thoughts appreciated as we are trying to diagnose the issue as it did create some complications for the hearings this morning.