I will have to roll back my change to obtain a crash log. I have not tested in a blank project, as this looks like it would only occur in World Composition, as if I look at the callstack, its calling UpdatePhysicsVolume when flushing level streaming on exiting a PIE session. So to answer the last question, its landscape in world composition, so I guess they would be sublevels, but the Physics volumes are in the sublevels, the persistent level is essentially blank, except for a player start.