It could be CX IT, and they are not very good.

It could also be processing. There might be financial implications for your previous change that have not been processed, even if the flight has been changed in your PNR.
I don't know what fare you used and its conditions. It is probably a corporate fare, but if it were a public flex PE there is a change fee of 100 plus a possible fare adjustment. These fares rarely allow for a negative fare adjustment (but if they do it will be paperwork). Until the accounting system has fully processed your rebooking (including paperwork for the credit card or arrangement with your TA/corporate account), the system will consider your transaction in process. You hold a confirmed booking on the new flight but the processing has not been completed. That happened to me on a couple of airlines even one with no change fee.
If your fare allow changes without any financial implications, then CX internal systems might still require processing if the surcharge/tax has changed and eventhough you are not paid back anything.