Move waypoint mouse click

I have a player with a child as a waypoint. My camera is a topdown camera (i would like for it to be pointing down at 45 degrees but i figure ill deal with that later). The problem is when i click down the waypoint is very jumpy and doesnt usualy move to where i want untill i click twice. any idea on how i could fix this? Thanks in advance

here is my code

function Update () { if (Input.GetButtonDown ("Fire1")) { var mousePos = Input.mousePosition; mousePos.z = 15;

     var objectPos = camera.main.ScreenToWorldPoint(mousePos);
   
    gameObject.transform.position = Vector3(objectPos.x, objectPos.y, objectPos.z);
    transform.root.gameObject.SendMessage ("Move");
  }

}