Elevator script problem

I recently made this elevator script, and it works great most of the time. However, sometimes when you get to the top it loops (jumps to the bottom and moves back up again). I've looked at the code but can't seem to find the reason why this happens. If you can find out way this is happening, please let me know. Thanks!

public Vector3 pointB;

 Vector3 startpoint;
 public float delay;
 public float speed;
 GameObject player;
 bool hasMoved;
 float playerPos;
 float thisPos;
 
 IEnumerator Start ()
 {
     player=GameObject.FindGameObjectWithTag("Player");
     startpoint=transform.position;
     hasMoved=false;
     while (true)
     {
         yield return StartCoroutine (PlayerTracking());
     }
 }
 IEnumerator OnCollisionEnter(Collision col)
 {
     if (!hasMoved)
     {
         yield return StartCoroutine("Move",delay);
     }
 }
 IEnumerator PlayerTracking ()
 {
     playerPos=player.transform.position.x;
     thisPos=gameObject.transform.position.x-transform.localScale.x/2;
     if (playerPos<thisPos && transform.position==pointB)
     {
         yield return StartCoroutine ("MoveBack");
     }
 }
 IEnumerator Move ()
 {
     GameObject.FindGameObjectWithTag ("Player").SendMessage ("MovingUp");
     var i= 0.0f;
     var rate= 1.0f/speed;
     while (i < 1.1f) 
     {
         i += Time.deltaTime * rate;
         transform.position=Vector3.Lerp(startpoint,pointB,i);
         yield return null;
     }
     if(transform.position==pointB)
     {
         GameObject.FindGameObjectWithTag ("Player").SendMessage ("DoneMoving");
         hasMoved=true;
         StopCoroutine ("Move");
     }
 }
 IEnumerator MoveBack ()
 {
     var i= 0.0f;
     var rate= 1.0f/speed;
     while (i < 1.0f) 
     {
         i += Time.deltaTime * rate;
         transform.position=Vector3.Lerp(pointB,startpoint,i);
         yield return null;
     }
     if (transform.position==startpoint)
     {
         hasMoved=false;
         StopCoroutine ("MoveBack");
     }
 }
 IEnumerator Death ()
 {
     yield return StartCoroutine("MoveBack");
 }

}