I've got a 2-4-1 Avios booking LHR-MAD-EZE return, all legs on IB in Business, obviously booked via BA. I was able to select seats a few months ago.

The flight is now in 14 days time but the seat reservations appear to have partially disappeared - only 3 of 8 selections remain.

There was a minor schedule change after booking, but no aircraft type changes as far as I am aware. I cannot access the reservation on the IB website because it says it was booked elsewhere. I can see the seat maps on the IB app but seat requests don't stick. I tried RJ but this shows me all seats being available and then throws up an error if I try to choose seats.

Any ideas how to check / confirm seat selection ahead of check in?