Walls, floor not loading

[Methusalem]

Hello Amnesians,

I've got a little problem with my planes and static objects.
Since I've added a new room with floor and walls to my mansion ( it's a big haunted mansion project ) , this specific room doesn't load anymore. Only the windows and doors are added to the map.
Do you have any clue ?
It's loading normally in the editor, but floor and walls of the room disappear in the real game.

Thanks in advance
( If you know the Cthulhu RPG story "The Black Forest Mansion", you can be looking forward for this custom map