On the second picture I have marked with yellow the part that is 'bulletproof'.
What is happening is that I can walk through the door without any problems. If I shoot at the area marked with yellow, bullets do not go inside the building, it is like bullets hit an invisible wall and stop.
If I shoot at the top half of the door, bullets go inside and hit the walls inside the building.
Another issue is that AI cannot see through the bottom half of door (the invisible wall). If I put an AI on one side of the door and I go prone on the other side, AI cannot see me.