UPDATE: Can be Damaged has to be turned off, when you do, it wont generate these arrows, it was not very clear in the documentation but now I am guessing they were here as a point of reference for guards to smash through them, as this is a custom NPC it does not smash buildings nor chase a player so it did not try to break the floor but was considered as a passage point.
Hope this helps someone, and hope the other bugs I mentioned get resolved as well