Zombies keep stopping in mid chase

I am trying the totally original idea of making a zombie game. I have a script to control the zombies, but they will constantly stop while they are attacking you. They pause for about a second, and then resume chasing you. It's probably something obvious, but this is my first project, so go easy. Here's my code:

 var walkSpeed = 3.0;
 var rotateSpeed = 30.0;
 var attackSpeed = 8.0;
 var attackRotateSpeed = 80.0;
 
 var damage = 10.0;
 var viewAngle = 20.0;
 var attackRadius = 2.5;
 var attackTurnTime = 1.0;
 var attackPosition = new Vector3 (0, 1, 0);
 
 var directionTravelTime = 2.0;
 var idleTime = 1.5;
 var attackDistance = 15.0;
 
 private var isAttacking = false;
 private var lastAttackTime = 0.0;
 private var nextPauseTime = 0.0;
 private var distanceToPlayer;
 private var timeToNewDirection = 0.0;
 
 var target : Transform;
 
 private var characterController : CharacterController;
 characterController = GetComponent(CharacterController);
 
 function Start () 
 {
     if(!target)
         target = GameObject.FindWithTag("Player").transform;
         
     yield WaitForSeconds(idleTime);
     
     while (true)    
     {
         
         yield Idle();
 
         yield Attack();
     }
 }
 
 function Idle()
 {
     while (true)
     {    if (Time.time > timeToNewDirection)
         {
             yield WaitForSeconds(idleTime);
             
             var RandomDirection = Random.value;
             if(Random.value > 5)
                 transform.Rotate(Vector3(0,20,0), rotateSpeed);
             else
                 transform.Rotate(Vector3(0,-20,0), rotateSpeed);
                 
             timeToNewDirection = Time.time + directionTravelTime;
         }
         var walkForward = transform.TransformDirection(Vector3.forward);
         characterController.SimpleMove(walkForward * walkSpeed);
         
         distanceToPlayer = transform.position - target.position;
         
         if (distanceToPlayer.magnitude < attackDistance)
             return;
             
         yield;
     }
 }
 function Attack()
 {
     isattacking = true;
     var angle = 0.0;
     var time = 0.0;
     while (angle > viewAngle || time < attackTurnTime)
     {
         time += Time.deltaTime;
         angle = Mathf.Abs(FacePlayer(target.position, attackRotateSpeed));
         move = Mathf.Clamp01((90 - angle) / 90);
         direction = transform.TransformDirection(Vector3.forward * attackSpeed * move);
         characterController.SimpleMove(direction);
         yield;
     }
     var lostSight = false;
     while(!lostSight)
     {
         angle = FacePlayer(target.position, attackRotateSpeed);
         if(Mathf.Abs(angle)> viewAngle)
         lostSight = true;
         if (lostSight)
             break;
             
         var location = transform.TransformPoint(attackPosition) - target.position;
         if(Time.time > lastAttackTime + 1.0 && location.magnitude < attackRadius)
         {
             target.SendMessage("ApplyDamage", damage);
             
             lastAttackTime = Time.time;
         }
         if(location.magnitude > attackRadius)
             break;
             
         if (characterController.velocity.magnitude < attackSpeed * 0.3)
             break;
             
             yield ;
         
     }
     isAttacking = false;
 }
 
 function FacePlayer(targetLocation : Vector3, rotateSpeed : float) : float
 {
     var relativeLocation = transform.InverseTransformPoint(targetLocation);
     var angle = Mathf.Atan2 (relativeLocation.x,
                 relativeLocation.z) * Mathf.Rad2Deg;
                 
     var maxRotation = rotateSpeed * Time.deltaTime;
     var clampedAngle = Mathf.Clamp(angle, -maxRotation, maxRotation);
     
     transform.Rotate(0, clampedAngle, 0);
     return angle;
 }