Lets make Lightmass EPIC (and understandable)

Hallo guys! I am reading this post since few weeks and I thought I was ready to test all I learned.
But i’ve encountered many problems I do not understand and I hope you can help me.

Take a look at the image please:

You can see the black surfaces around windows and doors and the pure black lines near the floor and ceiling. Anyone know how can I fix this? The weird thing is that this effect occures not on every window and door as you can see!
My previews tests, when I was creating a scene similar to the one people was training on in this post (some walls and obstacles) went almost perfect. This one is much worse and I dont know what I am doing wrong.
My lightmass are correct, double check that. Any change to lighmaps does nothing to fix theese effects. Also smoothing groups are ok I think.

Is it something about the lightning? (I used this tutorial to light this scene 2/)
Or maybe i’ts something with the model it self? I created it in 3ds max sometimes using extrudes and sometimes bridge feature to create holes (windows, doors).

Please help :slight_smile: