Box collider following incorrectly. (3d)

I have a game where you drag the enemies off the world but if the enemy touches the object you lose. Right now I attached a box collider to sense if a collision happens between the two but the box collider goes off course and flys towards the object no matter where the enemy is. I tried nothing with the box collider so far, also the enemy is a ragdoll. Here is a video showing what happened. - YouTube (sorry for the bad quality but at the end the box collider was on the white plane). Later I will post a better video.

Oh, you just have to adjust the size ._. If you still have any problems plz comment and I will try to fix it.