Host video thumbnail not showing in recording with screen sharing

Hi.

Usually when I host a meeting involving screen sharing, the recording includes both mine and the participant's video for the whole meeting (in thumbnail form while screen sharing). However, when I hosted a meeting yesterday, my (the host) video thumbnail did not appear in the recording when screensharing (though both host and participant faces appear when not screen sharing, as expected given I always use gallery view). 

Could the (new) participant in my meeting yesterday have had settings at their end that cause this to happen? They were not a co-host so I wouldn’t have thought so. Any idea would be appreciated.

Thanks,

Kelly.