Black area, not the lightmap

Hi all,

I’ve an issue with UE4.

I’ve a strange artefact in my scene. I tried to change Lightmap resolution, ( 512 - 1024 -2048 ), but it doesn’t work :confused:
It’s one sided mesh, so I tried to enable two sided in mesh and in a material, without results.

I attached a picture to illustrate my issue

Do you have an idea ?

No answer ? :frowning: