Navigation does not act as expected when using User Created Widgets in a scroll box

Child widgets that are marked as Is Focusable = True appear to sometimes be ignored if they are placed within parents who are set to Is Focusable = False.

1. Download the attached project
2. Open the attached project
3. Play in editor
4. Click the top button under the text "Works"
5. Press down on the Arrow key until the bottom button is highlighted
6. Click the Top button under the text "Broken"
7. Press the down arrow key to try and navigate to the bottom button
8. Notice that the widget instead looses focus

Expected: The Navigation would work the same on both sides and that the user would be able to navigate through the scroll box and out to the bottom button
Result: The second button in the scroll box appears to be skipped (even though it is set to Focusable) and the focus for the widget is lost