Bit of a mission to get this working against head but applied https://www.drupal.org/node/2369111 manually. The issue is that when a site uses language path prefix in the function globalredirectNormalizeAliases does not take into account the prefix returned the line at fault is $alias = $this->aliasManager->getAliasByPath($system_path, $this->languageManager->getCurrentLanguage()->getId()); as that returns the language prefix with it. Once stripped out further along the function $url = \Drupal::pathValidator()->getUrlIfValid($alias) also only ever returns the internal URL (node/x) and never redirects to the alias.