There have been issues like this for a while caused by latent occlusion queries. Occlusion queries are done a frame behind for technical reasons.
Tim is right that increasing bound scale will fix it in some cases, but you will be chasing your tail and eventually have to increase too many things using that method which will cause overall performance too drop eventually. A better solution is to have a sealed background mesh that encapsulates the playable area for any areas that are made out of tiny meshes jammed together. Usually if you are building more custom level geometry using 3dsmax this issue will not present itself.
The background mesh can be a very crude lowpoly bsp-like mesh. If your level is mostly a cave, the mesh can be really simple. If your level is more elaborate like a series of caves with a bunch of outside exits you need to put a little more work into it. We commonly do stuff like this for our levels for reasons such as preventing light leaking as well. Fixing occlusion isn’t the only reason to do that. Give it a black, lit material so that it can cast shadows as well to help with light leaking. Then make sure to set the lightmap res very low (4 or so) to keep it from impacting build times.