I booked a return to TXL on Expedia as 2 one-way fares came out cheaper than a ba.com HBO return. I expected the Expedia fares to be HBO (but as far as I can tell there is no way to know on Expedia?).

The flights showed up as HBO in MMB, but I could select a seat on the outgoing flight (only) . However now check in is open, I can't OLCI (the seat remains confirmed in MMB).

The bookings were listed in My upcoming flights on ba.com, but did not transfer to the Mobile app. The app rejected the booking references, but in fact later added the bookings (although OLCI is still not possible).

An odd glitch which I assume desk check in will resolve.