In unreal 5.4 I created some meshes using modeling tool(mostly cubes). For some reason some of those meshes (could be a simple box or a created Boolean mesh) were not showing on lumen debug display. Some rooms were light because of those “walls”. Most meshes did create those distance fields but few did not(they did but they were 0.0 MB or something). The meshes reappeared in lumen after I enabled nanite for them and rooms were dark as they should. You could check some of those debug views.