When you connect to the cms, the sitemap tool try to put you on your language, if not goes on the default one.
When you search for a content for sample (or anything with the ChoosePageFromSitemap) you can go on another site, but when you do so, it tries to put you on your language : but if your language does not exists it fails

The exepected behavior it that it goes on the default one, like the sitemap tool