I've been having this issue as well. When you call up your inventory, select DBS, interact with her and leave without doing anything removes any of the buttons on the lower half of the interface. I can sometimes get them back by either entering the save menu and then exiting again, or by hitting ESC twice, however I have been completely soft-locked a couple of times with DBS scenes (sadly I can't remember which) where i am unable to regain access to navigation buttons, etc...