Would you rather they flew planes with maintenance issues ?
I don’t disagree generally by the way, but they have a shortage of aircraft due to problems with their 787s
https://www.flyertalk.com/forum/british-airways-executive-club/2122071-ongoing-issues-ba7-ba8-tokyo-haneda-service-10.html#post35458191
This is interesting re on going issues BA seem to be having
It’s possible if they are moving passengers around, or a plane type has changed they’ve blocked all seat reservations while they sort it out. If you’ve got a confirmed booking & ticket I’d not worry for now
Also worth looking at alternative routes / flights on the same day. If you get bumped...