Constant Contact is sending wrong promo codes to recipient List

As the title suggests, when I uploaded a list with promo codes to Constant Contact, CC sent the wrong promo codes, which have no relation to the lists. Moreover, one of the email campaigns that I sent out had mixed-up promo codes from another list, and customers got the wrong promo codes. In the past, everything was working fine. Am I missing something? Can somebody help me with this issue?