Hi Amir, I believe its due to global illumination. I use the same settings as koola.
I also use these settings for lightmass.
As for UV lightmaps, the fbx importer from 4.5.0 onwards has a built in uv lightmap generator. But i think to really get good lightmaps there are just certain objects that cannot be unwrapped automatically and have to do it by hand, hence the forum post.
Example.
This cabinet is imported with the iv lightmap generated by ue4.
This is the lightmap
Look at the handle of the cabinet there seems to be some shadow glitch. Probably will need to touch up the uvmap but i am not sure exactly how. Lol.