Floor plane reflection For testing purposes I have created a simple HDRI with HDR Light Studio that is visible in the reflection of the box. 



Now I want a floor plane reflecting the exact box above without interacting with the scene at all. But the reflection on the box has changed when the floor is visible. 



In the "Objects"-Tab I can disable the glossy-rays for the floor so the reflection of the box looks as desired. But this way the reflected box won't show any reflections at all.



Is there an other workaround for it? Blender scene is added.
As for the reason why it is happening, it is because the main direction of where your HDRI's light is coming from is from the bottom right corner of your image, and the floor is blocking that.



In order to fix that, if you go to the node editor, change the view to world shader and add a mapping and texture coordinate node for your HDRI, you can adjust the tilt of the HDRI.  If you connect the generate output of the Texture Coordinate node to the input of the mapping node and the output of the mapping node to the input of the Environment Texture, then you can control the angle of the HDRI.



You can use the rotation values in the Mapping node to adjust the HDRI's angle.