Skybox is reflecting from game object in some devices?

I've noticed that after I build my game as an apk and import it into my Samsung Galaxy S5, I can partially see the skybox of my game on the background. It makes the background look kinda ugly. I've encountered the same issue in Bluestacks.

The picture above should give you a better idea.

On the left, you'll see the skybox that I'm using in the editor. It's just the default skybox preset by Unity.

After that, I created a Cube game object, re-sized it as a background and added a black material to it. In the Game view, it looks fine. This is shown in the middle part of the picture. Note that this is also the display in my Galaxy S3 as well as most other Android devices. This is the intended effect. So nothing wrong here.

The right part of the picture shows the problem that I'm dealing with. This is what the background looks like in Galaxy S5 and Bluestacks. As you can see, the skybox is partially visible on the "cube" background. I find it to be quite ugly.

Is there anything I can do so that the background does not appear as it does in the right part of the picture? Why is the skybox partially visible on the game object? This is bothering me.

If you're wondering what kind of material I'm using on the "cube" background, I'm just using a normal material with Standard shader. The Metallic and Smoothness of the material are both set to 0. The color of the material is black (000000FF). No texture added. All other settings are set to their defaults.