On 7th April a change was effected(1), removing a necessary conversion via the strtolower function while implementing new functionality in the search-redirect.php(2).
The client sides of the various portals send their names with the lead character in uppercase ("Wiktionary", "Wikisource"), however, the "in_array" comparison of the search-redirect.php(2) needs a conversion of these to lowercase, or there will be no matches and always a default to wikipedia.