I posted the same question and no one answered me. This seems to be a common issue with all WordPress/BuddyPress installs (I have a separate WordPress install and the same thing occurs), so it seems to be inherent in the responsive CSS code or something.
Doesn’t anyone have any advice, since it’s affecting so many of us?
And no, it was not due to a conflicting plug-in or a theme. Tests were done when the site was just installed with the default themes. The links shows up correctly on desktop, and on my Nexus 7 2013 (1200×1920 resolution) ONLY when it is in landscape mode, but not when it is portrait (empty, black bar is show). And the same empty black bar is shown on my Galaxy Note 3 (1080×1920 resolution) in both portrait and landscape. So it doesn’t seem to be due to just the horizontal resolution – but perhaps the the full (horizontal x vertical) resolution or something.