I think that the first thing to try is to go to the AY, QR or RJ websites, call up your booking and delete the current frequent flyer number. End the transaction. (Personally, I would then leave the website, and give the system half an hour or so.) Go back to the booking and re-insert the frequent flyer number. That might make AA tell BA that you are now a Sapphire and enable your free seat pre-allocation.