People have found that when you have a build that requires you to be inside a physical volume, you sometimes get "occlusion culling" in the 2d viewer (I don't know if this also happens in VR) when you move around in a scene. This means that part of the scene vanishes when you try to view from certain angles and positions.
I think this problem may arise from uploading objects that exhibit occlusion culling using the "add a collision mesh" slot.
upload object without physics.- call it object A
make a simple or transparent object (a cube, say) - call it object B. Then upload object B and attach the physics for object A in the "add a collision mesh" slot for object B.
If object A and object B have the same coordinates, then it is a simple matter to place them in the same location in a sansar scene.