I just gave the system a bit of a stress test - bought a Lat TATL ticket, moved it five times and then had to cancel it outright (all thanks to a disorganized client). In the process, I learned that if you check into a flight and then cancel the ticket it won't release your credits automatically, or at least it won't if a travel agent made the request. The system also managed to "lose" three credits in the process. There was no record of any transaction, but my available count was low.

On the positive side, AC was able to fix the canceled ticket while I watched and then re-applied the missing three credits a day later.