Trace Sets - Can't add to reflection exlcude list.

[Vizioen]

Something weird is happening or I'm not doing it right: I have a mirror that is reflecting a showerhead through the glass of the shower. But I don't want the showerhead to show in the mirror so I'm using trace sets for the first time ever.

Now I want to exclude both the showerhead and the glass from the reflection exclude list in the vray properties of the mirror. But it doesn't, for the life of it, want to "remember" that I also moved the glass in the exclude list. The moment when I close the list he's forgotten it. I've tried nearly everything. I've uploaded it the 3 objects here. Thanks y'all.

[Vizioen]

The solution seemed to recreate the mirror, I have no idea why it didn't want to accept the showerglass. The mirror used to be box114 and the glass box115. Maybe in a distant past they used to be copies or instances (but not anymore) and for some weird reason that's why he didn't accept it. Might be worth looking into if someone has nothing to do over lunch.