Does the "crew AA guns" buttom fuction correctly?
 

When I click it my crew does not get on the guns. I have to drag and drop them. I use RFB, am I missing something?

AA gun crew
 

You have to have the position manned at all times, whether they're needed or not. For example, if there's incoming aircraft, you can choose to "Engage," but unless there's someone on the gun, no one will automatically show up. Same with deck gun.
Hope that's the answer you need.