A small bug where a person can die twice (and appear twice in the graveyard).
So in one game I played, a Marshall revealed and lynched two people. The first person lynched ended up being a Jester. The second person lynched was 12, and he was one of the people who voted for the Jester's lynch. The next morning, 12 apparently died again because of Jester suicide. This made 12 appear twice in the graveyard (and die twice). I think it's a simple case of Jester suicides not making an exception for people who are already dead.