Shadow problems with static mesh?

Hi…

Shadows are quite hard to understand, I have several problems but I will start with this easy one…
I have this building, like a simple room, you can enter, and also go to the roof…

So I added an actor inside the room, and another in the roof… and this is what I see on the shadows:

The shadow that is printed on the roof ground, is also printed in the room ground… why that is happening? What do I need to change to avoid that?

In addition, I found this while in Shipping + Cooked mode, not debugging…