Some items do not show up

See for instance http://classification-explorer.noknot.fr/classification/nafr2/sousClasse/23_69Z/classification/nafr2/sousClasse/23_69Z

Problem comes from missing labels in english.

Test query:

PREFIX skos:http://www.w3.org/2004/02/skos/core#
PREFIX xkos:http://rdf-vocabulary.ddialliance.org/xkos#
SELECT ?clLabel {
http://stamina-project.org/codes/nafr2/naf skos:prefLabel ?clLabel
}

There's only a french label for the classification.

This query does not return any result, and I think it's related:

PREFIX dcterms: http://purl.org/dc/terms/
PREFIX skos: http://www.w3.org/2004/02/skos/core#
SELECT ?code ?label ?issued WHERE {
http://stamina-project.org/codes/cpfr21/cpf skos:notation ?code ; skos:prefLabel ?label ; dcterms:issued ?issued .
FILTER ( langMatches(lang(?label), "EN"))
}

So the page http://classification-explorer.noknot.fr/classification/cpfr21/details/cpf does not show up.