I used an ecredit to pay for a flight change last week, and not only did the remaining balance appear as a new ecredit with a new expiry date, 3 extra certificates also appeared all for the original amount and all with new expiry dates. I messaged Delta to advise they should review and remove the dummy certs, and they replied to say they had passed the info over to the relevant dept. and closed the ticket. The certs still show though. I now have the ethical dilemma of whether to ever try and use them.