This is normal on the map version that the F|A servers are running. Usually only affects the spawn floor of the building, but arty placed outside can sometimes reach the second floor
This is a physics problem when the truck enters the first floor. I can work on a fix so that the truck stops on the top of the hill until the door is blown (which would provide allies additional cover they desperately need on that section of the map) which would fix the arty on the second floor. The whole in the roof has been a problem since the maps introduction. Not sure if that is fixable, but most people don't know about it, like the roof access on some of the versions of the Aldernest map, which i believe should be on Hardcore because of the amount of players that play on it