script does not work when you open the Unity

I have a script to capture the height, width and distance from the camera. This script is associated with the Main Camera and works normally.

 using UnityEngine;
 
 public class GerenciarCamera : MonoBehaviour
 {
     public Camera camera1;
     private static float minX;
     private static float minY;
     private static float maxX;
     private static float maxY;
     private float distanciaZ;
 
     void Start()
     {
         distanciaZ = transform.position.z - camera1.transform.position.z;
         minX = camera1.ScreenToWorldPoint(new Vector3(0, 0, distanciaZ)).x;
         maxX = camera1.ScreenToWorldPoint(new Vector3(Screen.width, 0, distanciaZ)).x;
 
         minY = camera1.ScreenToWorldPoint(new Vector3(0, 0, distanciaZ)).y;
         maxY = camera1.ScreenToWorldPoint(new Vector3(0, Screen.height, distanciaZ)).y;
     }
 
     public static float MinX()
     {
         return minX;
     }
 
     public static float MinY()
     {
         return minY;
     }
 
     public static float MaxX()
     {
         return maxX;
     }
 
     public static float MaxY()
     {
         return maxY;
     }
 }
 

By reopen the project in Unity, it seems that the script stops working. To make it work, I remove it from the Main Camera, and readd again. This way works. What could be wrong? Bug?

Thank's