In practice the authority often asks for identity details, earlier documents, birth certificates, copies, contact with consular authorities or explanations why a document is unavailable. The key point is whether the request is specific and capable of being fulfilled.
Affected persons should document the steps they have taken: appointments, letters, evidence of enquiries, translations and replies from authorities. This matters if it is later alleged that departure failed because of lack of cooperation.
Vague allegations should not be accepted without review. Family records, spellings of names and old documents often create misunderstandings that need to be corrected in the proceedings.