The error mainly comes from the British NDC.
Action:
Not long ago a new payment processing platform was introduced: Introduction of changes to payments processing
With this new platform some new features were introduced also for the call centre colleagues. As we are informed they are able to check what was the reason of a payment rejection. So if an agent encounters an issue when they try to issue the tickets I advise them to call the contact centre (the NDC country specific numbers can be found on NDC Trade Support), then the colleagues should give information why they payment was not successful and they should be also able to assist with the ticket issuance.