Content not translated

The menu language of the Main navigation is set to Not specified. I add some text in the body field on a menu item in french and I translate this menu link in german. I set a new body text for this menu item in german. The body text is always displayed in french (also on the german pages) with {{ item.content }} in menu--extras.html.twig

Am I doing something wrong or is the translation of the body field not supported for the moment?