I think romullus was right.
You have a reflective material, if you want diffuse secular reflections use a very low glossiness value, like 0,1 or so, with 0,5 you may get visible reflections, plus use a lower reflection value, like 0,25.
Also why do you use a 2,0 value for ref IOR?
I think that could remove the reflections.
Cheers!