Defect of light between the meshes

I noticed that a light defect is created in my project. At the point where the two meshes come into contact this light effect is created.

I tried to increase the size of the meshes so that one passes through the other trying to eliminate the defect.

I have checked the normals of both meshes but they show no defects.

Can anyone suggest me a solution or can help me understand?

Don’t extend walls past each other in the corners, it causes other issues. Your walls need to have thickness and an outer surface, even if the outside isn’t visible you need something there to block the light properly. You can turn down the lightmap resolution for the outer surface if it’s not going to be visible, it just needs to cast shadows.

Thanks for the reply and advice.

The walls were thick but I still had this flaw.

I followed your advice by casting shadows like this …