I have the same problem.
I’m using Blender v2.7.4 and Unreal Engine v4.7.5. I have read everything I could, but I can not find the error. I attached pictures.
There is a small gap between the faces of the cube. I tried from Blender, different values of separation, but none works. As you can see the shadow is not correct when lighting is rebuilt. The Light map Coordinate Index is 1. I have two channels UV. The mesh is a simple cube without any modification.
I appreciate your help.
