System Information
Operating system: windows 10
Graphics card: GTX750 Ti

Blender Version
Broken: blender-2.80.0-git.dc3b5024be1a-windows64

Any material with a normal map eventually will become a "Emissive" object in the scene.
This is a old bug, is been there in the alpha and continue to anoying in the beta.

Exact steps for others to reproduce the error
First create a new material.
Put a normal image in a norma map node.
It works for some time.

After some time working on the scene the normal maps will transform the object in a giant lamp.
See the attached images{F6391676}