Have AA mental booked on domestic flight, trying to change online to different flight (AA flight number, operated by AS). After selecting desired flight website crashes with obviously wrong URL:

<< Check if there is a typo in www.aa.comnull07005a87-f465-467e-80c0-e62a55a >>

I tried multiple different options for AS codeshare flights and all the same. No problem with AA metal.

UPDATE: Spent half hour with agent on the Chat, they see availability, can book AS codeshare flights, but get internal error on the payment stage. Ahaha. Everything seems to be broken. Agent suggested to wait and try again .