If you import a static mesh to the editor, then open the mesh in the editor window of meshes to edit the materials etc.
And while you got the window open then click in the model on the content browser and import the LODs the LODs don’t show in the mesh window and if you close the dinwos an re open then the LODs are missing but if you place the mesh in the map you got 4 slots of materials for the mesh + LODs and if you now import another time the LODs with the mesh windows closed and then open the windows you got the mes + the other 3 LODs, but at place the mesh in the map now you got 7 or 8 slots of materials.
A quick fix at the moment for this is select the model in the content browser and press in re import and then you going to have only the real LODs and material slots.