Second problem, sometimes it gets into a weird state where the dropdown never appears and instead the shell's top bar becomes non-transparent and then transparent again on every keypress. That's partially a shell bug, but it must be our fault that the dropdown is not appearing. No clue why that's happening. (Shell bug is https://bugzilla.gnome.org/show_bug.cgi?id=790384.)

When this happens, the entry completion pops up after typing a few characters, and then *immediately* withdraws and stays withdrawn and does not return unless I play around with switching windows via the shell overview. Just using Alt+Tab doesn't seem to be enough.