How to reproduce:

1. Open new project
2. Import attached package simpleRepro.unitypackage
3. Open scene test.unity
- Scene contains a simple cube, plane and a few different light sources. The cube and plane have some coloured materials attached and both game objects are set to Static. All of the light sources are differently coloured and have their baking set to Baked. Ambient Occlusion is set to 0
4. Bake the lightmaps
- Note how the loading bar goes through a relatively long Bake AO process, which results in nothing as AO is effectively disabled.