Display errors when using Normal Map on other UV channel than UV0

I'm working on a simple DiffuseMap-NormalMap-shader for 3D meshes.

I need my normal map to be on a different UV channel than the diffuse map, so I cannot use the standard UV0 for both. However, the normal texture is displayed incorrectly on all of the remaining three channels, even though they all contain the correct unwrap. The texture is torn to pieces and partially flipped for no apparent reason.

This shouldn't be happening, right?

I should be able to use normal maps on UV1, UV2, and UV3 without any problems.