Hi Dekkuran,
This appears to be a UV problem. Even if it doesn’t seem like it could be, this is where I’d start looking first.
When you build lighting do you get any error messages after it’s done that says “Overlapping UVs”?
Also, can you post a screenshot of you lightmap UV (Channel 1) from the mesh editor? You can do this by toggling the UV button in the toolbar and changing the drop down to UV channel 1.
Also check in Maya, that you do not have any flipped or inverted faces in your UV.
Thanks!
Tim