Not sure if there is a more general issue but I booked last week an open jaw JFK-LHR-EDI/LHR-JFK. The transatlantic legs are on AA metal but it’s a BA ticket (to get eligible flights for my daughter’s renewal otherwise would have booked with AA). I got the AA record locator but for the first time I could not select any seat. Called AA and she was confused too but managed to assign seats that appear to have stuck to the booking but cannnot be changed on line. Very odd, usually don’t have a problem with BA codeshares before