I finally came up with an elegant solution to the paradox problem in my game. Say you open a door or raise an elevator for your other clone, then next time you don't. Getting that clone to gracefully detect, react to and recover from that paradox state wasn't easy, but now when they detect it they halt all playback until the paradox clears. If it doesn't then they'll just remain in that frozen state, but if the paradox does clear then they'll continue on their way as if nothing had happened. Sounds obvious but from a programming perspective it was incredibly complicated.