while exporting a scenery object with complex(4+ colliders) structure of the simple shape colliders, some of the colliders do not work and appear as white boxes in collisions debug. Colliders have unique IDs and linked to the LOD0, but it's impossible to predict which collider will not be exported correctly next time, it's pure random process. The only way to workaround is to export as many times as required to get all colliders to work.
I see the problem in 3ds max exporter, because the FS core engine handles the collisions in proper way
I use Multi File Exporting