I made a research before answering. First, In the case where Attestation is not seen as credible, it could be because there are no other supporting documents like (Marriage certificate, education transcript, birth certificate) accompanying the attestation. Remember before attestation is received, affidavit would have been sworn in the court with a proof of age and relationships. In the case where you have attestation and no other older document showing proof of age and relationship, the credibility of the attestation will be in question.
Solution
Submit any of the accompanying documents with LOE, and with a letter from NPC stating that the attestation documents are original. You will be 100% sure of nomination.