[Solved]Why doesn't my ScriptableObject based asset save using a custom inspector ?

So I made an asset system based on the ScriptableObject. I have several assets made this way and they all save perfectly but one. Some have custom inpector display, some have not.

My problem is that I can't identify why this one does not save. Every time I hit the Play button or change scene in Editor the asset is reset to default.
I tried to use EditorUtility.SetDirty(...), AssetDatabase.SaveAssets(), SerializedObject.ApplyModifiedProperties(), none of them have any effect.

Here is the asset that doesn't save :

 using UnityEngine;
 
 [CreateAssetMenu(fileName = "DefaultMap", menuName = "Terrain/Map")]
 public class FightMapData : ObjectData
 {
     [SerializeField]
     private int height = 1;
     public int  Height { get { return height; } set { height = value; } }
     [SerializeField]
     private int width = 1;
     public int  Width { get { return width; } set { width = value; } }
     
     [SerializeField]
     private TileData[][]    terrain;
     public TileData[][]     Terrain { get { return terrain; } set { terrain = value; } }
 
     public void ResizeTerrain()
     {
         if (terrain == null)
             terrain = new TileData[width][];
         else if (terrain.Length == width && terrain[0] != null && terrain[0].Length == height)
             return;
 
         TileData[][] terrainCopy = new TileData[width][];
 
         for (int i = 0; i < width; i++)
         {
             terrainCopy[i] = new TileData[height];
 
             for (int j = 0; j < height; j++)
             {
                 if (terrain.Length > i && terrain[i] != null && terrain[i].Length > j)
                     terrainCopy[i][j] = terrain[i][j];
                 else
                 {
                     Debug.Log("else,      height : " + height);
                     terrainCopy[i][j] = null;
 
                     if (terrain.Length > i)
                     {
                         if (terrain[i] == null)
                             Debug.Log("null");
                         else
                             Debug.Log("terrain[i].length <= j");
                     }
                     else
                         Debug.Log("terrain.length <= i");
                 }
             }
         }
 
         terrain = new TileData[width][];
 
         for (int i = 0; i < width; i++)
         {
             terrain[i] = new TileData[height];
 
             for (int j = 0; j < height; j++)
             {
                 if (terrainCopy[i][j] == null)
                     terrain[i][j] = null;
                 else
                 {
                     terrain[i][j] = CreateInstance<TileData>();
                     terrain[i][j].Copy(terrainCopy[i][j]);
                 }
             }
         }
     }

  

It's custom inspector :

 using UnityEngine;
 using UnityEditor;
 
 [CustomEditor(typeof(FightMapData))]
 public class FightMapDataEditor : Editor
 {
     private bool mapFoldout = true;
     private Vector2 scrollPosition;
 
     public TileData FillTileData = null;
 
     public override void OnInspectorGUI()
     {
         FightMapData fightMapData = (FightMapData)target;
 
         fightMapData.ResizeTerrain();
 
         EditorGUILayout.Space();
         fightMapData.Id = EditorGUILayout.TextField("Id", fightMapData.Id);
         fightMapData.Name = EditorGUILayout.TextField("Name", fightMapData.Name);
 
         EditorGUILayout.Space();
         fightMapData.Height = EditorGUILayout.IntField("Height", fightMapData.Height);
         fightMapData.Width = EditorGUILayout.IntField("Width", fightMapData.Width);
         
         EditorGUILayout.Space();
         mapFoldout = EditorGUILayout.Foldout(mapFoldout, "Map");
         if (mapFoldout)
         {
             EditorGUILayout.Space();
             FillTileData = (TileData)EditorGUILayout.ObjectField("TileData to fill Map", FillTileData, typeof(TileData), false);
             EditorGUILayout.BeginHorizontal();
             if (GUILayout.Button("Fill"))
                 fightMapData.Fill(FillTileData);
             if (GUILayout.Button("Fill blanks"))
                 fightMapData.FillBlanks(FillTileData);
             EditorGUILayout.EndHorizontal();
 
             EditorGUILayout.Space();
             scrollPosition = EditorGUILayout.BeginScrollView(scrollPosition, true, true);
             EditorGUILayout.BeginHorizontal();
             for (int i = 0; i < fightMapData.Terrain.Length; i++)
             {
                 EditorGUILayout.BeginVertical();
                 if (fightMapData.Terrain[i] == null)
                 {
                     EditorGUILayout.EndVertical();
                     continue;
                 }
 
                 for (int j = 0; j < fightMapData.Terrain[i].Length; j++)
                     fightMapData.Terrain[i][j] = (TileData)EditorGUILayout.ObjectField(fightMapData.Terrain[i][j], typeof(TileData), false);
                 EditorGUILayout.EndVertical();
             }
             EditorGUILayout.EndHorizontal();
             EditorGUILayout.EndScrollView();
         }
     }
 }

Here is an example asset that save perfectly :

 using UnityEngine;
 
 [CreateAssetMenu(fileName = "DefaultUnit", menuName = "Unit")]
 public class UnitData : ObjectData
 {
     public enum Classes { None, Soldier }
 
     [SerializeField]
     private Classes _class = 0;
     public Classes   Class { get { return _class; } set { _class = value; } }
 
     [SerializeField]
     private int level = 1;
     public int  Level { get { return level; } set { level = value; } }
 
     [SerializeField]
     private int baseHitPoints = 0;
     public int  BaseHitPoints { get { return baseHitPoints; } set { baseHitPoints = value; } }
     [SerializeField]
     private int strength = 0;
     public int  Strength { get { return strength; } set { strength = value; } }
     [SerializeField]
     private int dexterity = 0;
     public int  Dexterity { get { return dexterity; } set { dexterity = value; } }
     [SerializeField]
     private int luck = 0;
     public int  Luck { get { return luck; } set { luck = value; } }
     [SerializeField]
     private int speed = 0;
     public int  Speed { get { return speed; } set { speed = value; } }
 
     [System.Serializable]
     public struct WeaponRank
     {
         public WeaponData.WeaponType Type;
         public WeaponData.Rank Rank;
         public int Experience;
     }
     [SerializeField]
     private WeaponRank[]    weaponRanks = new WeaponRank[6];
     public WeaponRank[] WeaponRanks { get { return weaponRanks; } set { weaponRanks = value; } }
 
     [SerializeField]
     private bool    canMount = false;
     public bool     CanMount { get { return canMount; } set { canMount = value; } }
     [SerializeField]
     private int movement = 0;
     public int  Movement { get { return movement; } set { movement = value; } }
 
     [SerializeField]
     private ArmorData[] armorPieces = new ArmorData[4];
     public ArmorData[]  ArmorPieces { get { return armorPieces; } set { armorPieces = value; } }
     [SerializeField]
     private WeaponData[]    weapons = new WeaponData[4];
     public WeaponData[]     Weapons { get { return weapons; } set { weapons = value; } }
 
     [SerializeField]
     private HorseData   horse = null;
     public HorseData    Horse { get { return horse; } set { horse = value; } }
 
     [ExecuteInEditMode]
     public void Awake()
     {
         WeaponRanks[0].Type = WeaponData.WeaponType.OneHanded;
         WeaponRanks[1].Type = WeaponData.WeaponType.TwoHanded;
         WeaponRanks[2].Type = WeaponData.WeaponType.Polearms;
         WeaponRanks[3].Type = WeaponData.WeaponType.Archery;
         WeaponRanks[4].Type = WeaponData.WeaponType.Crossbow;
         WeaponRanks[5].Type = WeaponData.WeaponType.Throwing;
     }
 }

  

It's custom inspector :

 using UnityEngine;
 using UnityEditor;
 
 [CustomEditor(typeof(UnitData))]
 public class UnitDataEditor : Editor
 {
     private bool weaponsFoldout = true;
     private bool armorsFoldout = true;
 
     private bool weaponRanksFoldout = true;
 
     public override void OnInspectorGUI()
     {
         UnitData data = (UnitData)target;
 
         EditorGUILayout.Space();
         data.Id = EditorGUILayout.TextField("Id", data.Id);
         data.Name = EditorGUILayout.TextField("Name", data.Name);
 
         EditorGUILayout.Space();
         data.Sprite = (Sprite)EditorGUILayout.ObjectField("Sprite", data.Sprite, typeof(Sprite), false);
 
         EditorGUILayout.Space();
         EditorGUILayout.LabelField("Equipment", EditorStyles.boldLabel);
 
         weaponsFoldout = EditorGUILayout.Foldout(weaponsFoldout, "Weapons");
         if (weaponsFoldout)
         {
             data.Weapons[0] = (WeaponData)EditorGUILayout.ObjectField("Equipped Weapon", data.Weapons[0], typeof(WeaponData), false);
             data.Weapons[1] = (WeaponData)EditorGUILayout.ObjectField("Seond Weapon", data.Weapons[1], typeof(WeaponData), false);
             data.Weapons[2] = (WeaponData)EditorGUILayout.ObjectField("Third Weapon", data.Weapons[2], typeof(WeaponData), false);
             data.Weapons[3] = (WeaponData)EditorGUILayout.ObjectField("Fourth Weapon", data.Weapons[3], typeof(WeaponData), false);
         }
 
         EditorGUILayout.Space();
         armorsFoldout = EditorGUILayout.Foldout(armorsFoldout, "Armors");
         if (armorsFoldout)
         {
             data.ArmorPieces[0] = (ArmorData)EditorGUILayout.ObjectField("Head Armor", data.ArmorPieces[0], typeof(ArmorData), false);
             data.ArmorPieces[1] = (ArmorData)EditorGUILayout.ObjectField("Torso Armor", data.ArmorPieces[1], typeof(ArmorData), false);
             data.ArmorPieces[2] = (ArmorData)EditorGUILayout.ObjectField("Gauntlets", data.ArmorPieces[2], typeof(ArmorData), false);
             data.ArmorPieces[3] = (ArmorData)EditorGUILayout.ObjectField("Boots", data.ArmorPieces[3], typeof(ArmorData), false);
         }
 
         EditorGUILayout.Space();
         data.CanMount = EditorGUILayout.Toggle("Can Mount", data.CanMount);
         if (data.CanMount)
         {
             data.Horse = (HorseData)EditorGUILayout.ObjectField("Horse", data.Horse, typeof(HorseData), false);
             if (data.Horse == null)
                 EditorGUILayout.LabelField("Movement Bonus : 0");
             else
                 EditorGUILayout.LabelField("Movement Bonus : " + data.Horse.MovementBonus);
         }
 
         EditorGUILayout.Space();
         EditorGUILayout.LabelField("Statistics", EditorStyles.boldLabel);
 
         data.Class = (UnitData.Classes)EditorGUILayout.EnumPopup("Class", data.Class);
 
         EditorGUILayout.Space();
         data.Level = EditorGUILayout.IntField("Level", data.Level);
 
         EditorGUILayout.Space();
         data.BaseHitPoints = EditorGUILayout.IntField("Base Hit Points", data.BaseHitPoints);
         data.Strength = EditorGUILayout.IntField("Strength", data.Strength);
         data.Dexterity = EditorGUILayout.IntField("Dexterity", data.Dexterity);
         data.Luck = EditorGUILayout.IntField("Luck", data.Luck);
         data.Speed = EditorGUILayout.IntField("Speed", data.Speed);
         data.Movement = EditorGUILayout.IntField("Movement", data.Movement);
 
         int defense = 0;
         int weight = 0;
 
         for (int i = 0; i < 4; i++)
         {
             if (data.ArmorPieces[i] != null)
             {
                 defense += data.ArmorPieces[i].Defense;
                 weight += data.ArmorPieces[i].Weight;
             }
         }
 
         if (data.Weapons[0] != null)
             weight += data.Weapons[0].Weight;
 
         EditorGUILayout.LabelField("Defense : " + defense);
         EditorGUILayout.LabelField("Weight : " + weight);
 
         EditorGUILayout.Space();
         weaponRanksFoldout = EditorGUILayout.Foldout(weaponRanksFoldout, "Weapon Ranks");
         if (weaponRanksFoldout)
         {
             EditorGUILayout.LabelField("One Handed");
             data.WeaponRanks[0].Rank = (WeaponData.Rank)EditorGUILayout.EnumPopup("Rank", data.WeaponRanks[0].Rank);
             data.WeaponRanks[0].Experience = EditorGUILayout.IntField("Experience", data.WeaponRanks[0].Experience);
             EditorGUILayout.Space();
             EditorGUILayout.LabelField("Two Handed");
             data.WeaponRanks[1].Rank = (WeaponData.Rank)EditorGUILayout.EnumPopup("Rank", data.WeaponRanks[1].Rank);
             data.WeaponRanks[1].Experience = EditorGUILayout.IntField("Experience", data.WeaponRanks[1].Experience);
             EditorGUILayout.Space();
             EditorGUILayout.LabelField("Polearms");
             data.WeaponRanks[2].Rank = (WeaponData.Rank)EditorGUILayout.EnumPopup("Rank", data.WeaponRanks[2].Rank);
             data.WeaponRanks[2].Experience = EditorGUILayout.IntField("Experience", data.WeaponRanks[2].Experience);
             EditorGUILayout.Space();
             EditorGUILayout.LabelField("Archery");
             data.WeaponRanks[3].Rank = (WeaponData.Rank)EditorGUILayout.EnumPopup("Rank", data.WeaponRanks[3].Rank);
             data.WeaponRanks[3].Experience = EditorGUILayout.IntField("Experience", data.WeaponRanks[3].Experience);
             EditorGUILayout.Space();
             EditorGUILayout.LabelField("Crossbows");
             data.WeaponRanks[4].Rank = (WeaponData.Rank)EditorGUILayout.EnumPopup("Rank", data.WeaponRanks[4].Rank);
             data.WeaponRanks[4].Experience = EditorGUILayout.IntField("Experience", data.WeaponRanks[4].Experience);
             EditorGUILayout.Space();
             EditorGUILayout.LabelField("Throwing");
             data.WeaponRanks[5].Rank = (WeaponData.Rank)EditorGUILayout.EnumPopup("Rank", data.WeaponRanks[5].Rank);
             data.WeaponRanks[5].Experience = EditorGUILayout.IntField("Experience", data.WeaponRanks[5].Experience);
         }
     }
 }