I don't know if this is due to the update, but in tonight's game, I had several popout characters open for NPCs, and a player wanted to summon a fire snake. So, I dragged the snake to the map from the compendium, and it overwrote each of the popout characters (including a custom one) with the Fire Snake's stats. Reloading, including getting everyone to leave, and then reloading didn't fix it. Had to delete those characters and drag new ones in from the compendium. A pretty big bug, if it's repeatable.