requests logged on 2012-06-09 for hour 19:00
is correctly decoded (the "%C3%B3" is transformed to an accented "o"), whereas a request for
is not decoded and we're told the page doesn't exist.
As I noted at https://en.wikipedia.org/wiki/Wikipedia:Redirects_for_discussion/Log/2013_December_9#.5Cx22Weird_Al.5Cx22_Yankovic there's been a tremendous increase in the amount of this traffic reaching the WMF projects, from about one request per hour in September 2011 to millions of requests per day in November 2013.
Perhaps it would be desirable to transform "\x" to "%" before passing URLs to rawurldecode() so that these requests will reach the intended pages.