Bug Odd tab key behaviour

Pressing the tab key in any editor tab other than the inspector (lighting, occlusion, custom editor, etc.), brings the tab out of focus, instead of moving the focus to the next field/variable.

 

Update: Focus is actually directed to the correct field when pressing tab or shift tab, however the focused editor window is incorrect. Clicking inside the editor tab/window will result in the correct field being selected.

I've added a debug statement to one of my editor windows, and found out that the focused window changes to "Null" after pressing tab or shift+tab.

Code (CSharp):

1. Debug.Log(EditorWindow.focusedWindow);

If I press shift+tab right after pressing tab, the editor window comes back into focus (however pressing shift+tab and then tab or shift+tab twice does not do the same).