Hi!

In the process of working with shadows and reflections found trouble.
On picture 1 shows how the shadow falls on the floor. When we change the camera angle you can see the reflection from the light brightens shadow (picture 2), resulting in the shadow disappears.

Tell me how to avoid this?

Remove specular I can not because there are models that have a specular map. In the light of which specular zero defeats the purpose of specular map.

You should not use shadow.alpha.
You can use light.ambient.

Thank you.
The problem disappeared when I started using a normal map and specular.