I tried with other uvs, importing tangents/normals from maya, changing resolution of the lightmap, generating tangents/normals inside ue4, generating lightmap inside ue4 and importing from maya, etc…
wow thanks a lot. The problem is gone and the solution was exactly what you say. I only create a new lightmass map uv set into maya, click automatic mapping, separate all the faces and cut! so all the shells are “one uv island”.
Then i create a layout where all shells are separated 0.4 units (uv coordinates).
Then increment the resolution of the lightmap to 256 and its all.