NavMesh doesn't generate bounds around some static meshes

hey Sean,
I’ve been experementing with NavMesh’s details last days, but it didn’t give any results. I’ve also tried to change collision presets with no luck. Looks like the problem is in my custom made meshes.
Thank you!
https://drive.google.com/drive/folders/0B18txmDP0z31bUtNbkE3LTlZeGc?usp=sharing