The corner that is presumably supposed to connect to the watch star, is actually placed too far out connecting to nothing.
This happens 9 out of 10 page loads in latest Chrome on iPad (iOS 8.3), and also reproducible on desktop.
At http://en.m.wikipedia.beta.wmflabs.org/wiki/Alcatraz_Island, logged-out, after opting into Beta from the settings.
While not possible on mobile, when letting the page fully load and doing a window resize, the corner usually corrects itself. I guess the styles are computed prematurely and hitting a race condition.
Perhaps the distance can be computed relatively from the top right corner of the overlay (using the known width of the icon) instead of absolutely for from top left corner of the page container (which depends on a lot of variables only known at run time).