I don't know why it does that m8, think it happens to everyone, many times i can hear my rear gunner firing at an enemy plane, i switch views so i can take over the duties and...nothing happens i cannot make him shoot or anything as soon as i change views again he starts shooting again, at first i though he was maybe reloading but not so, best thing to do is rank your gunners up (if you have planes that need more then one man you need to buy the extra crew ranking points or they don't perform) what i mean is click on your "go to crew" button then go to "gunners" at the very top it says "number of experienced gunners" now if you are in a bomber that needs 4 crew and you only have bought one or two gunners your plane will or crew will not perform too good, you need to fill all these slots up,i know it can take quite a few Silver Lions maybe 240 each crew member but that is what you need to do, then when you have all your crew you really need to rank them all up in all the categories in the "Gunners" section and then probably best to leave them to shot enemies down themselves to be honest.