While running heroic Lords of Dread in a cross faction group, during the among us phase players of the same faction could not attack each other, and players of the same faction could heal/otherwise interact. So instead of everyone being hostile to everyone else, horde were still friendly to horde, alliance still friendly to alliance.
Reporting the same issue as you. Didn’t pay attention to what faction could attack which. But the phase would start out as everybody being attackable and sometime during the intermission a large portion of the people would turn friendly. We had to yeet the correct people off the edge to kill it.