SetActive in Editor script strange behaviour

Hello,

I have an editor script in which I automatically configure a scene each time I receive a new version from my 3D artist. It contains 100s of objects that need to be configured by adding scripts and filling the scripts with data stored in scriptable objects. This works fine. But I also need to enable/disable specific game objects. And there things are going strange.

Here part of my code:

 GameObject[] objects = Resources.FindObjectsOfTypeAll<GameObject>();
         
 foreach (GameObject o in objects)
 {
     // Do stuff
 
     // TEST SETACTIVE
     if (o.name == "KetelVervangen_01")
     {
         string objectType = "";
         if (PrefabUtility.GetPrefabParent(o.gameObject) == null)
             objectType = "Prefab: ";
         else
             objectType = "GO in hierachy: ";
 
         Debug.Log(objectType + o.activeSelf);
         o.gameObject.SetActive(true); // THIS IS NOT WORKING AS EXPECTED
         Debug.Log(objectType + o.activeSelf);
     }
 }

The output of my "Test SetActive" block (where I test 1 of 100s objects) is: - Prefab: True - Prefab: True - GO in hierarchy: False - GO in hierarchy: True

So it seems that, based on the activeSelf property, SetActive is actually doing it's thing, but my game object in the hierarchy itself stays inactive.

Any clues?