2D game spotlight issue with floor tiles,2D game spotlight floor tiles get different brightness

In a 2D top-down game that uses lighting, the light is a spot light that lights the player and his surrounding, some of the floor tiles looks different, it's like they get a brighter color than other tiles.

I've tried to play with the light settings, when I set the render-mode to "not-important" the problem disappear, but it looks horrible when set to "not-important", I get the same result when changing the "Pixel light count" to zero in the quality settings. The floor tile's shader is "sprites/diffuse".