Still seeing this in 4.13.1.
Details (in case different - not a reimport but an initial import): Import FBX from 3DS Max. Item is a modeled (not cloth) item of clothing with 3 LODs, each with a single UV channel/texture, skeleton same a character already loaded (no LODs at present). LOD0 has one material element, but LOD 1 and 2 both have 2. Isolate on second shows no visible mesh. Placing a texture in 1st element of LOD1/2 sometimes also populated second element, sometimes doesn’t. If click delete under second element, also clears first element. Did the fix above cause a knock on issue here?