Problem with MoveToWaypoint

Hi! In my game I want my NPC move from one point to another and therefore I created the following script based on an example I found on the web. But the NPC is not having a uniform motion, and doesn't stop for a while when it reaches the target position as I wanted. He is always rotating and moving around the map. Also, appears the error: "Script error: Update () can not be a coroutine." Someone can help me solve this problem please?

     var pointB : Vector3;
     private var pointA : Vector3;
     var moveSpeed : float = 10.0;
     
     var waitTime : float = 5.0;
     private var waitTimer : float;
     
     //enum State {Waiting, Moving}
     private var currentState : State;
     
     function Start () {
         pointA = transform.position;
         
         currentState = State.Moving;
     }
     
     function Update () {
         switch(currentState){
             case State.Waiting:
                 Wait();
                 break;
             case State.Moving:
                 if(transform.position==pointA)
                     MoveObject(transform, pointA, pointB, 3.0);
                 if(transform.position==pointB)
                     MoveObject(transform, pointB, pointA, 3.0);
                 break;
         }
     }
     
     function MoveObject (thisTransform : Transform, startPos : Vector3, endPos : Vector3, time : float) {
         var i = 0.0;
         var rate = 1.0/time;
         while (i < 1.0) {
             i += Time.deltaTime * rate;
             
             thisTransform.position = Vector3.Lerp(startPos, endPos, i);
             thisTransform.LookAt(endPos);
             //yield; 
         }
         if(thisTransform.position == endPos)
             currentState = State.Waiting;
     }
     
     function Wait() : void{
         waitTimer += Time.deltaTime;
         if(waitTimer > waitTime){
             waitTimer = 0.0;
             currentState = State.Moving;
         }
     }