I let my users have access to the theme and they quickly found something odd going on 
I use the Custom Header Links theme component and with the other theme I use (Material Design), as you reduce the browser window width when you reach the point that that links would overwrite the site logo the logo shrinks, eventually becoming pretty tiny, e.g.
With Fully the logo doesn’t shrink so eventually you get this…
Custom Header Links removes the links and displays the topic title when viewing a topic. The topic title also overwrites the logo in narrower browser widths, although eventually the logo is completely removed which resolves the issue.
I’m not sure if this is a Fully or a Custom Header Links issue, but I’m starting here as CHL does work OK in the other theme.