Hi,

Language fallback is implement only to translate content, but not to translate design. If you defined languages fallback like this:

• fre-FR
• eng-GB
• ger-GE

Contents have correctly the fallback. But on design, if you omit to translate some part in french, you don't have this fallback
Should be easy to fix with a compiler pass and a little:

$translator->setFallbackLocales( array( 'fre-FR', 'eng-GB', 'ger-GE' ) );

http://symfony.com/doc/current/components/translation/introduction.html