Null Reference after finding object already

well i have a problem with a script using a function of another script and coming up with null reference after i already got a debug.log to tell me that it found the object.to test the script i have it call a function from the other script both in the start and the update functions. and the function works fine for the start but when it gets to the update the script lost its reference and changed it to null. here is the script:

 private PlayerScript playerscript;
     PlayerScript playerz;    
     
     
     void Start () {        
         PlayerScript playerz = FindObjectOfType<PlayerScript>();
 //        
         playerz.DEDE();
     }
     
     // Update is called once per frame
     void Update () {
         playerz.DEDE();
     }

this is the error i get

and all the other script say to do is this function:

 public class PlayerScript : MonoBehaviour {
 
 public void DEDE(){
         Debug.Log ("Found Player");
     }
 }

so if anyone could please answer me why this is happening i would be so appreciative. Please and thank you.