I've been having some issues... with rotating entities. It doesnt even work for armor stands :o So I summon a minecart that has been rotated, and it like, flips out and then un-rotates into a position facing west, and upright. I have also tried to rotate mobs, the only thing it will rotate, is the head, and it will only rotate up and down, not side to side. The body of the mobs will never move, they will only face south. Im not sure if this is a bug, or if it is intended, to remove making spheres out of rotated minecarts, and indirectly removed the rotation of all entities.