I have a problem with lightmap baking. They look a little weird, I don’t know what it could be, strange effects as I show in the image.
Could you show us the lightmap uv of the problematic mesh please?
So yes, THAT is causing the problem!!
The uv contain overlapping areas! And because different parts of your mesh gets the same lighting information from the map: it will be inaccurate!!
You can either fix it in your 3d app, you’re bringing your meshes from or you can generate lightmap uvs by Unreal!!