Problem with landscape material lighting and normal maps

I’ve created a complex material wich uses allegorithmic substance textures and landscape layers to blend the different textures.
As you can see in the screenshots below I have a problem when the normal map channel is activated and has a texture connected. Without normal map the lighting is correctly displayed, but as soon as I had a normal map the lighting gets a lot darker but only in some zones.

Does anyone know how to overcome this problem?
I’ve already tried by disabling the normal maps baking by lightmass, using a dynamic sun light and adding a flat normal map to the shader.

Thank you,

Without normal map

With normal map

Without normal map

With normal map

Maybe the normal map is way to powerful, can you post it?

Or it is not being sampled as a normal map. When you select the normal map nodes in the material, do they say “normal” under type?

Problem resolved!
It was the “Use DXT5 Normal Maps” enabled in the project settings. I’ve disabled it and now it’s all ok!

Thank you guys!