Editor GUI object field stops working

code:

 aa = (anchor)EditorGUILayout.ObjectField("Anchor", aa, typeof(ScriptableObject), true);

when it works it works but then randomly for no reason itll stop working (the drag and drop no longer alows me to drop anchors in it) so when that happens i changet the 'true' at the end to 'false' or vice versa and boom problem solved.... why?