@ Kenomica
I used the auto-generate for Channel 0, but now it’s an exact copy of channel 1. It did remove the issue of turning pitch black, but the shadowing is not quite right:
It’s not terrible except for the weird shadow pattern on the bottom right. The same mesh at a different location has a similar problem. I suppose if there is no way to fix this in UE4 I could go to Blender, although it seems odd considering I made this shape using two cube brushes in UE4. Would I be better off remaking the entire mesh in Blender?