4 lines of code makes untiy crash

These lines of code to make random.range not repeat numbers makes unity crash after playing for a while. I removed these lines of code below and it didn't crash.

 if (RandomQuestionIndex == Pastquestion && repeat == true)
         {
             while (RandomQuestionIndex == Pastquestion)
             {
                 RandomQuestionIndex = 
                 Random.Range(0,notAnsweredQuestions.Count);
             }
         }

Whole code:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using TMPro;
 using System.Linq;
 using UnityEngine.UI;
 public class TrueOrFalseQuizManager : MonoBehaviour
 {
     private int totalquestions;
     public TextMeshProUGUI scoreText;
     private int QuestionsWrong = 0;
     public GameObject EndGameScreen;
     private bool EnteredIEnumerator;
     private bool EnteredIEnumerator2;
     public Animator CanvasAnim;
     private bool repeat = false;
     private bool End;
     public Image image;
     private int Pastquestion;
     private int RandomQuestionIndex;
     public TextMeshProUGUI tmpText;
     public QuestionHolder[] questions;
     private QuestionHolder currentQuestion;
     private  List<QuestionHolder> notAnsweredQuestions;
 
     void Start()
     {
         notAnsweredQuestions = questions.ToList<QuestionHolder>();
         RandomQuestionIndex = Random.Range(0, notAnsweredQuestions.Count);
         Pastquestion = RandomQuestionIndex;
         currentQuestion = notAnsweredQuestions[RandomQuestionIndex];
         tmpText.text = ("" + currentQuestion.Fact);
         image.sprite = currentQuestion.QuestionImage;
     }
     private void Update()
     {
         
         if(notAnsweredQuestions.Count == 0 && End == false)
         {
             End = true;
             Debug.Log("End");
             StartCoroutine(EndQuiz(1));
         }
     }
     
     
     IEnumerator EndQuiz(float time)
     {
         
         if (EnteredIEnumerator2)
             yield break;
 
         EnteredIEnumerator2 = true;
         yield return new WaitForSeconds(time);
         //code after delay
         totalquestions = questions.Length;
         QuestionsWrong = totalquestions - QuestionsWrong;
         if(QuestionsWrong < 0)
         {
             QuestionsWrong = 0;
         }
         scoreText.text = "" + QuestionsWrong + "/" + "" + questions.Length;
         EndGameScreen.SetActive(true);
         EnteredIEnumerator2 = false;
     }
     IEnumerator NewQuestion(float time)
     {
         
             if (EnteredIEnumerator)
                 yield break;
 
             EnteredIEnumerator = true;
 
             yield return new WaitForSeconds(time);
             RandomQuestionIndex = Random.Range(0, notAnsweredQuestions.Count);
         /*if (RandomQuestionIndex == Pastquestion && repeat == true)
         {
             while (RandomQuestionIndex == Pastquestion)
             {
                 RandomQuestionIndex = Random.Range(0, notAnsweredQuestions.Count);
             }
         }*/
         Pastquestion = RandomQuestionIndex;
         if (notAnsweredQuestions.Count > 0)
         {
             currentQuestion = notAnsweredQuestions[RandomQuestionIndex];
         }
             tmpText.text = ("" + currentQuestion.Fact);
             image.sprite = currentQuestion.QuestionImage;
             repeat = false;
             // Code to execute after the delay
 
             EnteredIEnumerator = false;
         
     }
     public void CorrectPressed()
     {
         if (currentQuestion.IsTrue == true)
         {
             Debug.Log("Yup");
             CanvasAnim.SetTrigger("True");
             if (End == false)
             {
                 notAnsweredQuestions.Remove(currentQuestion);
                 StartCoroutine(NewQuestion(1));
             }
         }
         else
         {
             Debug.Log("WRONG");
             QuestionsWrong += 1;
             CanvasAnim.SetTrigger("NOPE");
             repeat = true;
             if (End == false)
             {
                 StartCoroutine(NewQuestion(1));
             }
         }
     }
     public void FalsePressed()
     {
         if (currentQuestion.IsTrue == false)
         {
             Debug.Log("Yup");
             CanvasAnim.SetTrigger("True");
             if (End == false)
             {
                 notAnsweredQuestions.Remove(currentQuestion);
                 StartCoroutine(NewQuestion(1));
             }
             
         }
         else
         {
             QuestionsWrong += 1;
             Debug.Log("WRONG");
             CanvasAnim.SetTrigger("NOPE");
             repeat = true;
             if(End == false)
             {
                 StartCoroutine(NewQuestion(1));
             }
         }
     }
 
 }