Stranges reflections

Hi guys, I’m new in Unreal and I got reflections on my materials that I don’t understand.
I have these white borders that appears on my “mirror” test materials (color: white, metalness: 1, roughness: 0).

The problem is that I have the same reflections on all my materials, and I don’t know from where it come.
Does that come from a bad setting of my sky sphere/light ? Or it’s a normal behaviour, and I’m missing something ?

Thanks for you help.

You may need to modify the Specular input with a scalar parameter or possibly a bit more complex for the wood/metal gate. Hold ‘s’ and left-click in an empty area of the material graph to create a scalar node.

Indeed, this white reflections on the metal come from the specular that I didn’t fixed, but I have still no idea for the reflections on the two first images.