Roll a Ball Tutorial, ball is flying up after a lot of movements

Questions & Answers
1

I am following the roll a ball tutorial, when I move the ball and collide it with the walls. The ball
stops, ok, but when I keep moving the ball around the play area. The Y position suddenly increases.
What causes this, is this just a setup issue? below is my code for Fixed update.

 private void FixedUpdate()
    {
        float horizontalMove = Input.GetAxis("Horizontal");
        float verticalMove = Input.GetAxis("Vertical");
        Vector3 destination = new Vector3(horizontalMove, 0.0f, verticalMove);
        rb.AddForce(destination * speed);
    }
2

Just solved it by myself. In the Player RigidBody set Constraints on Y.