"Add Freeze Frame" only freezes background clip?

I want to end my film projects with a freeze-frame of the final scene as background for the end credits. But when I click "Add freeze frame" it only freezes the background clip; not the additional layers of film, titles etc.

I can't find anywhere in the Help files how to freeze the whole thing - please advise if this is possible and, if so, how to do it.

Thank you!