Splotchy Mesh after Light build

Hello All,

I am just a Beginner in Unreal Engine and Following a tutorial in Archviz interior and encountered a wierd uneven lightmass build on a object. I had detached the Poly, Reset Xform, recompute normals or import normals and tangents . Did everything that i could do but still not getting the point . Please have a look and guide me in the right direction. .