how to fix normal of a shader after scaling with a factor of -1 I am making a door made of two sliding panels (I have simply made one panel, duplicated it and scaled it by -1 to make the second one)
As you can see, the flipped one get a weird color, I guess it is due to something happening with his normal when I scaled it by -1

Here is the same panels but without the normal map linked in the node editor and they look similar. I have also applied the scale of the object (the two panels have a scale of 1)
here is the simple node I use for the normal.

any idea how to fix it?
First set your normal map to be non-color, then apply scale on the copied door and recalculate it's normals (Alt+N in Edit Mode)