on my dev wiki (set to Kurdish - ku):
Notice: First alias 'Dara_kategoriyan' for Categories conflicts with first alias for CategoryTree [Called from SpecialPageFactory::getAliasListObject in /Library/WebServer/Documents/php-master/includes/specialpage/SpecialPageFactory.php at line 307]
the alias for Special:Categories needs to be different from Special:CategoryTree. (set on translatewiki)