Hi Tim, which Blender version did you use? (assuming you used Blender that is, but it if not it shouldn’t matter as I believe the bug is in the LOD Importer code itself). I’m asking so we’re on the same page when I send you a test file.
PS: To recap, the duplicate materials do not show up in the Static Mesh editor itself but they are visible when you place a static mesh in the map. More importantly they manifest internally; i.e. any material operation relying on index like mesh->GetMaterial(i) or mesh->CreateDynamicMaterialInstance(i) won’t work logically because of the duplicate materials messing up the index order.