At a random guess, the AA segment is probably complicating things here. AA uses Sabre whereas QR and many other oneworld airlines use Amadeus. Having flights span different GDS systems is slamdunk source of frustration for most airlines when processing any change to a ticket. It's not an excuse, just statement of fact. QRs own IT is also probably at fault as well, but Amadeus+Sabre is rarely going to work well.