Black faces after building lights

Hi, I have been using ue4 for a while now, and this is the first time I have seen this problem. Each step (thread+riser) on my stairs is a separate mesh. Basically It is just copy and pasted, so they all have the same uvs, lightmaps, Lightmap density and mesh settings. But when I build the lights some faces just render completely black.

Hi!

It’s “always” a lightmap error! Maybe when you duplicated your meshes in your 3d app the normals got flipped! …also could be duplicated faces looking at your screenshot…
But it’s almost 100% a lightmap issue! /could be missing, wrong channel is set…

I meant to post a reply to this months ago but I totally forgot. I got it fixed. It was a problem with lighting + reflections setup and the metallic panels on the steps. Originally I was using only static lights and a lot of them. Other people have had similar problems with static lights + Metallic materials. Why metal surface get very dark in static light - Rendering - Epic Developer Community Forums Anyway I just simplified my lighting setup. I used 6 stationary lights to provide the main source of light and a few static lights here and there to highlight some details. Also I setup proper reflections