Colisions dont work when rotated.
Maybe i found why some objects cant colide in sandbox: Cleared the mesh, rotate 90º, ready to export, no colisions. When i dont rotate, it can colide.
The mesh i used is Ferruginous bridge by "Admiral Kamikase". (I deleted all components, and used only floor and walls of the bridge.)
Maybe it help you guys making this splendorous program.
Sorry for my poor english, i have learned by myself and im not good.