were u still waiting for a response?
anyway, that happens to me too, but the way i fixit is to have in all LOD's which have the model, go to
Structure>Topology>Find Components
This will make a list of all the components in the model, to get rid of one, say if it is a fence or camo net, which bullets can pass through, then just go to the list, select the component, component xx, then right click on it and go delete,
i hope this helps u
ohhh, nearly forgot, make sure there is a set mass in the Geo LOD.
Lt. Shitkilla