Did you go into the material settings and uncheck the “Tangent Space Normal” option?
Oh and it looks like you are using a spline for each individual link? If so I wouldn’t expect spline thicken to be completely seamless when the camera rotates around, there will always be a little bit of interpolation at extreme angles and tight radius curves like you have. In the forum post you linked, those pipes were using a much larger curve radius which helps avoid artifacts, but even for that one if you were to rotate the camera around facing the curve at the right angle you could cause an artifact… but I would just use a real model if it was for an important shot or a non-background element.
I would probably make it a straight up strip without polys for the chains and have a second side profile slice present to provide thickness.