[From FF forum, not yet confirmed]
So, the first thing is that when you deploy vickers in bunker at Argub Bdawa in Siegie of Tobruk map you can't enter it. It seems deployed too low.
The second one is that you can't exit the deployed weapon in many bukners or buildings, no matter which side you try to exit it. Either the fixed exit point is not needed here or it's too restricted.
(Happened to me in those small sandbag bunkers, as well in that one on screen (I alwyas deploy it in the middle of free space). Haven't tested all the bunkers though.)
I had some sort of the same problem. I wanted to mount the Lafette on a balcony and point it into a certain direction. First thing going wrong was it deployed backwards, into the opposite direction. Then, when I entered it, I couldn't exit anymore, hearing a *dud* sound everytime I tried. I had to suicide to get out of it.