public int variable not updated in inspector for two scenes in Unity

I have five scenes in my Unity Project/Game. The first one is start scene (Build Index = 0) and remaining four are the levels of the game as (1,2,3,4). The logic is such that when the user moves from one scene to the next one, a new scene appears and previous scene is removed from the list. The order in which scenes appear is randomized. I did this by using a Singleton. This works perfectly fine. What I also want to do is, when a new scene is loaded the public int advancement = 8; checks for the current scene. For example, when I press play and the run project starting from Scene 0, in the Inspector I see advancement = 8;. I press button to load next scene. A new scene (lets say Scene 2) is loaded and in inspector I see advancement = 4; as I proceed in the game the advancement decreases as 3, 2, 1. This C# code works fine on my laptop. However, when I copied the the script in a different Unity Project on a different laptop. The code is working only for two scenes i.e., Scenes with Build Index 1 and 3. For Scenes with Build Index 2 and 4 the public variable advancement = 8 in the inspector and is never updated.

Can someone help me troubleshoot this?

Please see the code below.

 using UnityEngine;
 using UnityEngine.SceneManagement;
 using System.Net;
 using System.Net.Sockets;
 using System.Text;
 using System;
 
 public class BRIRToMax : MonoBehaviour {
 
     private static int localPort;
     private string IP;  // define in init
     public int port = 8051;  // define in init
     public int advancement = 8;
     
 
     // "connection" things
     IPEndPoint remoteEndPoint;
     UdpClient client;
 
     void Start()
     {
         
       IP = "127.0.0.1";
       port = 8051;
 
       remoteEndPoint = new IPEndPoint(IPAddress.Parse(IP), port);
       client = new UdpClient();
 
       int currentSceneBuildIndex = SceneManager.GetActiveScene().buildIndex;
       SendCurrentSceneBuildIndexToMaxMSP(currentSceneBuildIndex);
      
 
     }
 
     public void SendCurrentSceneBuildIndexToMaxMSP(int buildIndex)
     {
         // The UDP stuff to send to MaxMSP
         byte[] data1;
         Debug.Log("Build Index =:" +buildIndex);
 
   
         
         if (GameObject.Find("ButtonNextScene"))
         {
             
             Debug.Log("Remaining Scenes = " + (SceneAdvance.instance.remainingScenes-1));
             advancement = SceneAdvance.instance.remainingScenes;
      
         }
     
         try
         {
             if (advancement == 3) 
             {    
                 
                 byte[] welcome = Encoding.ASCII.GetBytes("H");
                 client.Send(welcome, welcome.Length, remoteEndPoint);
             } 
             
             else 
 
             {
 
                 Debug.Log("Do not trigger the toggle");
 
             
             }
 
             switch (buildIndex)
             {
                
                 case 1:
                     data1 = Encoding.ASCII.GetBytes("Q"); //Sc2_3500
                     client.Send(data1, data1.Length, remoteEndPoint);
                     Debug.Log("Q");
                     break;
 
                 case 2:
                     data1 = Encoding.ASCII.GetBytes("W"); //Sc2_1500
                     client.Send(data1, data1.Length, remoteEndPoint);
                     Debug.Log("W");
                     break;
 
                 case 3:
                     data1 = Encoding.ASCII.GetBytes("E");//Sc1_3500
                     client.Send(data1, data1.Length, remoteEndPoint);
                     Debug.Log("E");
                     break;
 
                 case 4:
                     data1 = Encoding.ASCII.GetBytes("R");//Sc1_1500
                     client.Send(data1, data1.Length, remoteEndPoint);
                     Debug.Log("R");
                     break;
             }
         }
         catch (Exception err)
         {
            Debug.Log(err.ToString());
         }
 
     }
 
 }