Issue with light

Hi everyone , that my first post here and the first problem i encounter . Please pardon my english …
I will try to explain the most i can .
So im using the 4.20 version, i have downloaded the free horror engine project and all work fine , i buy the classic mansion projet and work fine , but when i migrate something ( i mean map from each in each other) its seem dark everywhere only in my mansion level and not in other map. My issue is a black square show in my editor viewport and on my player viewport , that is not about pawn or something other , i have try to turn off and delete all post process and nothing fix my probleme . Here a link Who show my probleme Classic mansion issue - YouTube
As we can see if i move very fast my camera or the déplacement,the light appear around the corner but if i stop to move the dark comeback to everywhere. I have talk with the Author of the classic mansion but he cant find a way to fix it .
-I have look each world seting and that the same everywhere
-turn off and delete post process is useless about to fix the issue
-delete world light and all light stuff dont change anything
-if i migrate the classic mansion map the issue come back
-if i migrate level into classic mansion map the issue come back
-there nothing on my player caméra Who can create this ‘shadow’
If i forget something about my issue please tell me and i’ll try to put more specific thing i can try .
About my computer is a i5 with descent graphic card ans 8go of Ram (i know is not really good but i can play on kite demo … so i dont think that a probleme with my computer)
Edit:i just see if i change the quality of shadow on low and i take low the level issue is fix, so can it be about graphic ressource or something ?or directly a bad setup of shadow ? I come back to epic graphic i see my world great and its directly become black

After you migrated the mansion level did you build light?

In addition to that,. If the lighting required a plug-in or any C++ there’s a good chance they didn’t migrate properly