In the Top Tier 4 challenge it will alternate which top row crusaders can be used every 100 levels. It would appear there is some type of bug occurring when it switches as the game window will go black and game will freeze requiring a force quit of the game. Starting it up again will start back at the point where it crashed with no apparent loss. It then will be fine again till the next 100 level change. From what I can tell the game won't crash if you have a auto clicker on a unleveled and unavailable top crusader. I guess suddenly having a crusader in the formation at the point of change solves its problem. It does not however seem to work with just leaving a couple of out clickers on two crusaders one of each change. I assume this has to do with crusaders only being automatically added to the formation when they are first leveled up.

As it stands a annoying bug but not game breaking