Hmm OK I see what is happening here. FinalDestination is given
https://ru.wikipedia.org/wiki/%D0%A1%D0%B2%D0%BE%D0%B1%D0%BE%D0%B4%D0%BD%D0%BE%D0%B5_%D0%BF%D1%80%D0%BE%D0%B3%D1%80%D0%B0%D0%BC%D0%BC%D0%BD%D0%BE%D0%B5_%D0%BE%D0%B1%D0%B5%D1%81%D0%BF%D0%B5%D1%87%D0%B5%D0%BD%D0%B8%D0%B5
instead of
https://ru.wikipedia.org/wiki/Свободное_программное_обеспечение
For the first case we end up escaping the %sign… Hmm will need to figure out the format given to FinalDestination because the url passed to it is sometimes not escaped.