1) What happened
Emissive material doesn't lightup nearby objects

2) How can we reproduce it using the example you attached
The nearer emissive object gets to another object, the less light is projected from it onto nearby object.
1. Place object with emissive material next to another object (about 0.5 units away or less).
2. Bake the scene
---> There is not enough light goes from the source object onto its neighbour.
Expected - the closer emissive object gets to another one, the more light it'll produce onto the surface.
Currently it works OK with larger distances (further away - less light, nearer - more light), but at some close distances, behaviour changes.
See attached project for an example of the distance, where the projected light amount (from the emissive cube to the nearest 'wall') doesn't look right.