Camera properties jitter in OnSceneGUI

Hi there, so, I've got an Editor Script in which I have a code:

 [CustomEditor(typeof(TestTest))]
 public class TestTestEditor : Editor
 {
     public void OnSceneGUI()
     {
         Debug.Log("OnSceneGUI: " + SceneView.GetAllSceneCameras()[0].orthographicSize + "\n");
     }
 }

And the output for this fragment is:

 OnSceneGUI: 294.4149
 OnSceneGUI: 294.1218
 OnSceneGUI: 294.4149
 OnSceneGUI: 294.1218
 OnSceneGUI: 294.4149

And so on... Do you have an idea what causes this and how to eventually fix this? It messes up with my custom level editor in which I need precision. Scene View is set to 2D.

Any help would be much appreciated.