Problem with Armature Collision

I think it’s a bug, but I won’t lose anything for asking.

My characters have Collision only on feet. And when I change the place of the center of the Armature and change the Radius of Collision, the character flies away when it reaches the ground.
Can I repair it? Is there any alternative script for Collision?

umm dont use an armature for collision. use a cube and parent the armature to it.

The character still is flying away.
Can anybody make a tutorial teaching how can I a good collision?