World Composition blurring map

Hello,

I am sorry for the mistakes but I am not english.

I have troubles using world composition. So, I would like to use world composition with levels that I already have.
What I have done :
I have created a folder "world composition. In it I created a level named “persistent level” that have nothing else than a sky and lights. I enabled world composition.
With world composition I tested added several NEW levels and it was working well. Now I would like to add in it my own level.
So, I copy my map into the folder world composition but when I open the window where I can see the different loaded levels, then my map doesn’t appear correctly. A large space of the window is taken by a sky.

Like this :

So I thought that I comes from the sky (I was using ultradynamic sky). So I decided to copy my original map, delete the sky in the copy, and copy it (again) in world composition. I thought that it will solve the problem but it doesn’t : now in the window where I can see the different loaded levels, my map is still the same (with a sky above it like in the previous screenshot)…

Does someone know why I have this problem and can explain me how to solve it ?
(If you ask, my level is loaded and all is saved and it happened even if I reboot unreal engine)

Thank you in advance for your answers.

Best regards