Webinar Presenters are Showing up as squares, not fullscreen

[Odjur]

We're having an issue where webinar presenters are showing up as small squares when the webinar is viewed on a phone. I've verified this on both an iPhone13 and iPhone SE. What happens is a single presenter takes up the whole screen as expected. As soon as a second presenter joins both of the presenter screens go from 16:9 to 1:1 and there is empty space on about 1/3 of screen. If one of the presenters leaves, the single presenter who is remaining is still in a square and now about 2/3 of the screen is black. Everything looks fine in the desktop environment and on a tablet. Almost all of my users are joining from a phone though so this is a big problem. The picture attached shows what I mean.