Sparql query - Multiple entries for the same level and the same lang

The following query returns duplicated results (with same lang). Is it normal ? In the application, I updated this query to return distinct results.

PREFIX skos:<http://www.w3.org/2004/02/skos/core#>
PREFIX xkos:<http://rdf-vocabulary.ddialliance.org/xkos#>
SELECT ?level ?depth ?label
WHERE {
  <http://stamina-project.org/codes/cpav21/cpa> xkos:hasLevels/rdf:rest*/rdf:first ?level .
  ?level xkos:depth ?depth ; skos:prefLabel ?label .
} ORDER BY ?depth