The stables thread doesn't imply one building. There is a cowshed, a horse stable, Sally's pigsty, probably Raiga's kennel area, maybe a sheep enclosure, tack sheds, equipment stores, all kinds of actual buildings within the single thread, so I don't see a problem with Musco raping Sally in her pigsty while in another building Amy deals with Kanami and the two couples do not know of each other's presence.