Ok lets try something different. Save and backup your scene first for in case of any accident. And then open a notpad file then go to your level > select every object with CRTL+A > copy with CTRL+C > open notepad file and paste them with CTRL+V and save it. Now you are able to setup your scene in another level by reversing this process( copy from note pad to editor) if you dont change your directory. Now open a blank level > copy everything from the notepad file and paste in new level. Just wait i can take some time depends on level. If it’s done without crashing or error check everything on the level for be sure. Next this step is a bit confusing if you are doing it for the first time. Select your wall static meshes and press right mouse button there should be an option “MERGE ACTORS” and click on it. And do the same settings as shown below. And click merge actors button. Choose the directory to save it and wait until its done.
Now delete wall on your scene which you merged and bring the merged to your scene. Build lighting. And lets see what will happen. If you confuse to follow steps about merging actors go to this - YouTube
Goodluck…
