It is a cube (not plane)! UE cube. I just scaled down its thickness a bit (0.15 along X-axis).
Yes. Try it with a cube on a cube, and it works, right? So it’s not the light.
Could you give a link to the FBX maybe…?
Yes, I get that. But if you replace your wall with another scaled cube, the light problem will not happen. Ergo, it is something with your wall…