@razenwing: A bit late, but I just saw this. Re. the guy entering your session in the first place, that has happened to me on both Friends- and Invite-restricted settings. Not sure why. The worst one was one guy joining, another entering as I’m removing the first one, repeat with the second one… all the way up to 5 guys total, and just inexplicable.
I was left wondering why my non-public setting(s) was admitting total strangers into a session whose sole occupant was someone not on their friends list.
