Normalmap makes everything "shiny"

Hello everyone,
When i bake a Normalmap in Blender and use it, it makes the whole mesh shiny and reflective and
creates other issues like visable seams/patches.
Not at first but after renaming it or using a copy of the same normal map, then the issue becomes visable.

Even if use a random asset that i did not make myself and replace one of its normal maps with the same, just renamed
normal map it creats the issues.
(Cycles/Blender issue)?

They also appear when I import the Mesh and Textures into an gameengine like UE4.
That makes me wonder if there are informations in the mesh or textures that cause this problem.
Some settings i have missed in Blender?
Some Images

Thank you for your help

can you post the file? maybe flipped normals or some weirdness w/ the UV?

You set the renamed Normal to RGB and not Non-color…
which should only affect Blender and not UE4…but maybe it carries over… if not then it is mesh problems compounded by the metallic shader,