A donor updated their expiration date and their next payment was successful, but then it seems the next payment attempt used their old expiration date. How/who changed the expiration date?
The expiration date was likely changed by BBMS Credit Card Updater. The expiration dates are stored in a separate "Updater" system that is managed by the Credit Card companies. This system is separate from what the companies use to authenticate the cards. The CC company would be responsible for adding the new expiration date in to the Updater system. If there's new information available for the card next time the recurring gift is charged, then their next payment will be successful.