cac:PaymentMeans[cbc:PaymentMeansCode='30' or cbc:PaymentMeansCode='58']/cac:PayeeFinancialAccount[BR-50]-A Payment account identifier (BT-84) shall be present if Credit transfer (BG-17) information is provided in the Invoice.
Hitting this rule in production? Paste the invoice into the validator or wire the API into CI so it never ships broken again.