This happens at ports. Nothing new. It has been done for years. It is just been abused more in the last month or so by a few players.
The port offers a few buildings that can be entered when they have been bombed in a tank or other GV, When the building gets reconstructed, the GV inside cannot be destroyed by GV fire but like the three story building problem. They can shoot out of the building.
Jimmy can this be easily fixed by making these building indestructible like the big, indestructible building? Unfortunately, side swapping may offer more opportunities to abuse this flaw in the game.