character controllers without collider climbing each other

I am using the flow path finding solution on the asset store and trying to figure out why character controllers without colliders are able to climb each other if one of them is made to have a higher radius. In this package, there is a goal position set for the character controllers and they are given a move command(characterController.Move) every frame only. The only transform modification that happens is a shift of Y down to the floor each frame. There is a bunch of them and they move in a nice pack respecting each others boundaries well. However when I adjust the radius of one of them, to make a larger character, whenever the pack stops moving the bigger guy gets on top of the smaller ones. In the scene view these character controllers draw as if they have a collider but there is none shown in the game object or its chidlren. They don't even have rigid bodies. I am assuming there is some kind of hidden one with a character controller that allows it to move around the map. It acts as a capsule and character controller has a radius and height field. I have tried setting the slope limit down to near 0. However I cannot tell if they are actually climbing over their smaller brethren or being pushed up by people underneath. Anyone know what might be going on here?