Light bleeding even inside a closed box

I have scene setup with only one box (imported=>blender=>fbx=>ue4) and one directional light. I could see light on certain edges (as marked by the red arrows), any help to fix this?
this is inside the box.
See the image attached.

Yeah I’ve seen this as well. But just build lights and it should disappear.

Yeah. That’s just a prebuilt lighting thing. It’s a function of how the lighting system works. Build the lighting and get back to us if it’s still there. Alternatively, clip the meshes through each other a tiny bit if it’s still happening.

Yes building light makes it disappear.

Thanks, things are fine after building light.

Apparently giving the right answer doesn’t warrant an “Accepted” :’)

Yes, your was the first right answer, but didnt knew how to set it as the right answer. Was going to see to it but someone else marked the other post.