Trying to purchase round trip LCA-SEA, one direction in business, another direction premium economy. BA gives me error message after selecting flights. AA tells me that fare is not available after selecting same flights. This is regardless of dates and flights as long as I choose flights with cheapest promo fares.

Two years ago I had exactly the same problem and had to call to ticket, which took very long time to do manually, then it took equally long time to change date when I had to move return flight. I was assured it was temporary glitch which would be fixed.

Two years later - same problem.