How to solve error transform.position assign attempt for 'Car' is not valid. Input position is { NaN, NaN, NaN }.

In my game i have a car following a waypoint system, everyting seems to work perfectly but after a random amount of time my AI car stops moving and gives me the error transform.position assign attempt for 'Car' is not valid. Input position is { NaN, NaN, NaN }. This is the code i am using. Any help in solving my problem would be much appreciated.

 var path : Array;
 var pathGroup : Transform;
 var maxSteer : float = 15.0;
 var wheelFL : WheelCollider;
 var wheelFR : WheelCollider;
 var wheelRL : WheelCollider;
 var wheelRR : WheelCollider;
 var currentPathObj : int;
 var direction : float;
 var distancefrompath :float = 5.0;
 var maxTorque : float = 50.0;
 var currentSpeed : float;
 var topSpeed : float = 50.0;
 var decellerationSpeed : float = 10.0;
 var steerVector : Vector3;
 
 function Start()
 {
     rigidbody.centerOfMass.y = -3.5;
     GetPath();
 }
 
 function GetPath()
 {
     var path_objs : Array = pathGroup.GetComponentsInChildren(Transform);
     path = new Array();
     
     for (var path_obj : Transform in path_objs)
     {
         if(path_obj != pathGroup)
         {
             path[path.length] = path_obj;
         }
     }
     Debug.Log(path.length);
 }
 function Update()
 {
     GetSteer();
     Move();
 }
 
 function GetSteer()
 {
      steerVector = transform.InverseTransformPoint(Vector3(path[currentPathObj].position.x,transform.position.y,transform.position.z));
     var newSteer : float = maxSteer * (steerVector.x / steerVector.magnitude);
     direction = steerVector.x / steerVector.magnitude;
     wheelFL.steerAngle = newSteer;
     wheelFR.steerAngle = newSteer;
     if (steerVector.magnitude <= distancefrompath)
     {
         currentPathObj++;
         
         if (currentPathObj >= path.length)
         {
             currentPathObj = 0;
         }
     }
 }
 function Move()
 {
     currentSpeed = 2*(22/7)*wheelRL.radius*wheelRL.rpm* 60/1000;
     currentSpeed = Mathf.Round(currentSpeed);
     if(currentSpeed <= topSpeed)
     {
         wheelRL.motorTorque = maxTorque;
         wheelRR.motorTorque = maxTorque;
         wheelRL.brakeTorque = 0;
         wheelRR.brakeTorque = 0;
     }
     else
     {
         wheelRL.motorTorque = 0;
         wheelRR.motorTorque = 0;
         wheelRL.brakeTorque = decellerationSpeed;
         wheelRR.brakeTorque = decellerationSpeed;
     }
 }