I have a projet with only FR as available language
When resources are indexed, the full field is indexed in all available languages. So in my case, only 'full_fr'
When searching on documents, no language is specified (language is null). By default, the FullTextQuery will search on default language which "en" => full_en
So no documents are found
First fix will be to specified the language search according the current sitemap language
Second fix will be to set a language of indexation as a project configuration parameter :INTRANET-211