Inconsistent Lightmap Baking

When baking light maps, I get inconsistent results from self illuminated light sources.

In the attached image, the same models (purple blobs) and materials are used, yet only the models on the right are lighting up the ground around them. The models on the left are not illuminating correctly.

Has anyone encountered this problem?

have you marked both models as static and are really sharing the same material? For testing purposes, you could try do delete the left one and duplicate the right one in the inspector (or vice versa). Then, if it works, it was a problem with your settings (what i suppose)

Yes, they are both marked static, yes they are sharing the same material. Yes, they were created by duplicating the group of models (notice they have the exact same layout).