Argument is out of range. Parameter name: index

I have a tough problem for some days now. Therefore I made a test project with only the needed code for the problem. Everyting works fine when I run the programm except sometimes. Normally I get this in my console:

 Up:id1
 UnityEngine.Debug:Log(Object)
 GameScript:BuildDeck() (at Assets/Scripts/GameScript.js:69)
 GameScript:Start() (at Assets/Scripts/GameScript.js:26)
 Down:id1
 UnityEngine.Debug:Log(Object)
 GameScript:BuildDeck() (at Assets/Scripts/GameScript.js:69)
 GameScript:Start() (at Assets/Scripts/GameScript.js:26)

And then down till id8.

At the bottom I have:

 test7
 UnityEngine.Debug:Log(Object)
 GameScript:BuildDeck() (at Assets/Scripts/GameScript.js:75)
 GameScript:Start() (at Assets/Scripts/GameScript.js:26)

But the problem lies at the piece of code generating that. Sometimes I get the error: ArgumentOutOfRangeException: Argument is out of range. Parameter name: index System.Collections.Generic.List`1[System.Int32].get_Item (Int32 index) GameScript.BuildDeck () (at Assets/Scripts/GameScript.js:74) GameScript.Start () (at Assets/Scripts/GameScript.js:26)

I really don't know why I get that sometimes. Read alot on wrong arrays etc. but as far as I know everything is ok.

I use the generic List instead of ArrayList, because it's better. And I need a list for my contain method.

My code is:

 import System.Collections.Generic;
 
 var cols:int = 4; // aantal kolommen
 var rows:int = 4; // aantal rijen
 var totalCards:int = cols*rows; //totaal kaarten
 var matchesNeededToWin:int = totalCards * 0.5; //benodigde paren
 var matchesMade:int = 0; //startscore
 var cardW:int = 100;
 var cardH:int = 100;
 var aCards:Array; //Card array
 var aGrid:Array; // dealt card array
 var aCardsFlipped:ArrayList; //flipped cards array
 var aHuman:List.<int>;
 var playerCanClick:boolean;
 var playerHasWon:boolean = false;
 
 function Start ()
 {
     playerCanClick = true;
     
     // Initialize the arrays:
     aCards = new Array();
     aGrid = new Array();
     aCardsFlipped = new ArrayList();
     aHuman = new List.<int>();
     BuildDeck();
 }
 
 function BuildDeck ()
 {
     var totalHumans:int = 8; // 8 needed humans (16 humans total)
     var card:Object; // reference to a card
     var id:int = 0;
     
     while (aHuman.Count < totalHumans)
     {
         var humanNum:int = Random.Range(1,17); // random humans 1 t/m 16
         if (!aHuman.Contains(humanNum))
         {
             aHuman.Add(humanNum);
         }
     }
     
     /*
     for (var humanNum in aHuman)
     {
         Debug.Log("human:"+humanNum); //print List aHuman
     }
     */
     
     
     
     for (k=0; k<totalHumans; k++)
     {
         var aHumanParts:Array = ["Up", "Down"]; // 2 human parts
         id++;
         
         for (l=0; l<2; l++)
         {
             var someNum:int = Random.Range(0, aHumanParts.length);
             var theMissingPart:String = aHumanParts[someNum];
             
             aHumanParts.RemoveAt(someNum);
             
             card = new Card("human", theMissingPart, id);
             //card = new Card("human", humanNum, theMissingPart, id);
             aCards.Add(card);
             //Debug.Log("human", humanNum, card.img+":id"+id);
             Debug.Log(card.img+":id"+id);
             //Debug.Log("Part:"+theMissingPart);
         }
         //aHuman.RemoveAt(humanNum);
     }
     var human:int = aHuman[humanNum];
     Debug.Log("test"+human);
 }
 
 class Card extends System.Object
 {
     var isFaceUp:boolean = false;
     var isMatched:boolean = false;
     var img:String;
     var id:int;
     var human:String;
     
     function Card(human:String, img:String, id:int)
     {
         this.human = human;
         this.img = img;
         this.id = id;
     }
 }