I don’t know if you messed with the anti-aircraft engagement distance values based on the caliber of the anti-aircraft guns, but the Vickers-Terni 40/39 autocannon works and is always the first to fire, but the 13.2mm machine guns don’t. It’s extremely annoying because I have to take the anti-aircraft controls every time I need to fire and defend myself from the planes.
EDIT: I noticed that the 13.2mm machine guns are not even firing at vessels even though I gave them orders to fire at both vessels and aircraft.