Following on from my post here, i’ve put together a test project to show the problem. See if you can get the objects with a red dot on them to lightmap properly! I’ve deliberately increased ambient occlusion so that the lack of lightmapping on these objects is obvious.
Whenever some objects are wrong and others are right, it’s almost certainly an error in the lightmap uvs of those objects that are wrong. Lightmap uv’s must be unique, no wrapping, no overlapping, no zero area triangles.
In this case the error was that the object’s didn’t have correct UV’s in channel 0. The lightmap UV’s were fine. What’s weirder is that the thicker ones are just scaled versions of the same mesh yet they work.