Custom Editor: 2D-Array loses all data when entering play mode. 1D-array doesn't. What's going on?

So here's a weird one: I have this very simple class called script. It has 2 boolArrays. One 2D and another 1D array.

using UnityEngine;

 public class Script : MonoBehaviour {
 
     public bool[,] boolArray2D = new bool[10,10];
 
 
     public bool[] boolArray1D = new bool[10];
 }
 

I also have this Custom Editor Script which is supposed to modify the 2 arrays.

 using UnityEngine;
 using UnityEditor;
 
 
 [CustomEditor(typeof(Script))]
 public class CustomScriptInscpector : Editor {
 
     Script targetScript;
 
     void OnEnable(){
         targetScript = target as Script;
     }
 
     public override void OnInspectorGUI(){
 
         EditorGUILayout.BeginHorizontal ();
         for (int y = 0; y < 10; y++) {
             EditorGUILayout.BeginVertical ();
             for (int x = 0; x < 10; x++) {
                 targetScript.boolArray2D [x,y] = EditorGUILayout.Toggle (targetScript.boolArray2D [x,y]);
             }
             EditorGUILayout.EndVertical ();
         }
         EditorGUILayout.EndHorizontal ();
 
 
         EditorGUILayout.Space ();
 
 
         for (int x = 0; x < 10; x++) {
             targetScript.boolArray1D [x] = EditorGUILayout.Toggle (targetScript.boolArray1D [x]);
         }
 
     }
 }

This is what it looks like:

It's super super basic, but here is the problem: When entering play mode, changes I made to the 2D-array in the custom inspector disappear and changes to the one dimensional stay there. Is this a bug or am I just stupid?

( I shouldn't need to mark anything as Serializable because everything is public and standardt-types. I also tried several approaches, with if(GUI.changed && !Application.isPlaying){ EditorUtility.SetDirty(targetScript); EditorSceneManager.MarkSceneDirty(EditorSceneManager.GetActiveScene()); } but to no avail ): )

Any help is appreciated!