Ender Dragon breaks my world

When I spawn an Ender Dragon in the over world no matter the coordinates, the dragon will go to x = 0 z =0. She will destroy any block until it hit 0 , -62, 0, then she will take all the physics with her, then she will slip through bedrock. Every time I load back into the world, it keep repeating the same thing, but the dragon will be much closer to kill the world.