Metal black falloff change direction

Hi all,
I’m working on a material for an interior wall. This wall must have some kind of metal look. I copied some bits of the blueprint from the standard metal material, and on one side it looks good:

However, on the other side it shows almost completely black:

I changed the metallic value from 1 to 0.9. This made it a little brighter but still doesn’t solve the odd falloff on the model. Does anyone have any idea on how to direct this black falloff downwards? Any other ideas are also very welcome.

I found the answer myself in the meantime. Apparently my scene was missing a reflection sphere. After adding this, the black shade disappeared.