Workaround found:
Adding a directional light with light on and energy zero will remove the flickers, however the normal map is now "enlighted" even in the dark.
Directional light + ambient light leads into massive problem while lighting simple quads/sprite3ds (not black but different shades). So I removed the ambient light and added a second omni light on the player with large radius and low energy to get back a semi-ambi light.
