You remember, there was a bug in rtMedia 3.6.14 …
… now with 3.6.15 I still have de-activated rtMedia for BP Profiles and for BP Activity Stream - and I’m not using lightbox.
If I activate rtMedia for bbpress the problem is back: click on “Edit” of an attachement in a BP Group Forum. That will bring you to the BP Profile of the user who uploaded. And that way the Media component is available / visible in the user profile. You should find a way to “stick” in the bbpress forum while editing an attachement.