Here is a small sample showing that, if you comment out the roughness value everything works as expected
Thank you in advance.
Interesting. Thinking of it, I can only assume that it’s because if you set a value for the metallic workflow, it kicks in and overides/oversees reflectivity, as it is not part of the metallic workflow. Then, you would need to work it from the metallic and reflectance, could it be ? cc @Evgeni_Popov
If you don’t set neither metallic, roughness or metallicTexture, you are in the glossiness/specular workflow. As soon as you set one of these 3 properties, you switch to the metallic/roughness workflow. So, materials 1 and 2 are in the glossiness/specular workflow, whereas materials 3 and 4 are in the metallic/roughness workflow.