Any idea why the names of participants 2 and 8 appear as their username (login id) and not full name as for other participants? But their names on the participants list on the left bar are correctly displayed as their full names.
I've seen sometimes similar error, maybe not the username but that the name is presented with %20 instead of space and similar. Do you see the same issue every time for the same users or is it only some times?
The Large Gallery view is created in Teams servers, so it is only one video stream that comes to your computer. In regular gallery view you get one stream per user. So in this case I think it is some problem on the Teams servers that are creating the Large Gallery view stream, that is why you can see the full name in the participant list.
It was a while ago you posted this, it might be better for you now after a couple of weeks or do you still see the same problem?