Unity 5.4.0 for some reason, when baking shadows, uses a processor of 1%, and the process takes a very long time. How can you deal with this? Screenshot of the window "Lighting" tab Scene:
The scene is small: a corridor of 100-150 polygons measuring 12x2x1 meters.

Lightmap settings?Scenetab. And how big is the stage? And the version of unit 5, and then what are the numbers? - Alexey Shimansky