This same thing has recently started happening to me. Each time I cancel award travel, I see a flight credit in my wallet for the cancelled flight and have to call to have the miles reinstated and taxes refunded. Has anyone found a fix for this? I think AA may be doing this intentionally to deter frequent rebooking (at a lower mileage rate) - are others who experience this problem rebooking award travel frequently?
It's also interesting that a flight credit is being issued because the terms and conditions of using a flight credit state "Valid for: Non-Award Bookings."