clearing var in GO after updating

Unity Engine
1

I made a custom inspector in unity to fill item collections.
but there is a problem, every time I change a line of code, unity updates and resets all previously filled fields and objects
for example, there is such a window. it sets borders that are impassable along the edge of the terrain

this window changes the data in the script

[System.Serializable]
[DisallowMultipleComponent]
public class GameArea : MonoBehaviour
{
    private static GameArea _instance;
    public static GameArea Instance()
    {
        if (_instance == null)
        {
            _instance = GameObject.FindObjectOfType<SuperTerrain>();
            if (_instance == null)
            {
                _instance = new GameObject("Terrain", typeof(SuperTerrain)).GetComponent<SuperTerrain>();
            }
        }
        return _instance;
    }
    private void Awake()
    {
        DontDestroyOnLoad(gameObject);
    }
    [SerializeField] public Vector2 MinCorner { get; private set; }
    [SerializeField] public Vector2 MaxCorner { get; private set; }
    public void SetCorner(float xMin, float xMax, float yMin, float yMax)
    {
        DeleteOldCorner();
        MinCorner = new Vector2(xMin, yMin);
        MaxCorner = new Vector2(xMax, yMax);
        CreateCorner();
    }

and every time i’m deleted the old borders with hands (because the links to them are lost) and open the first window to enter the data again.

2

You can’t use SerializeField on properties. You need to serialize the backing field, use [field: SerializeField]