My seat map was unavailable for about 5 days leading up to online check-in. I managed to check-in on-line for my return MIA-LHR, which then preceded to want my passport info and a US address again, even though i'm on the return leg to the UK. I then tried to change seats and it timed out on me. Having logged back in it, it is refusing to change my seats or show me the seat map and says I should try later or at the airport. BA's IT systems are just hilariously bad.