Noticed that when narrowing the browser window enough to trigger the "phone" layout the dropdown starting with "Library catalogue" is moved to after the search field (living with "All libraries"). That layout is fully reasonable on phones, but when restoring to full size (on at least opac-search.pl and opac-detail.pl) the original layout is not restored. The bug appears in Safari and Chrome on OSX. Tried it on some demo installations to see that it's not related to CSS in our specific installation. I've not had the time to research if it's an issue with browser rendering, bootstrap or implementation in Koha.
I believe this issue has been resolved.