Weird effect when adding a normal map

Hello

I’m making a funfair simulation game but I have a problem. The ride that I’m doing have a floor divided in several parts. All these parts have the same material, but when i add a normal map to that material, each part have a different colour.

This is how the model looks like without adding the normal map (with a material that uses only a texture).

And this is how it looks like when I add the normal map. Each part have a different color, but all of them have the same material.

How can I fix it?

Did you import your normal map texture as a normal map?99462-inspector2.png