I have a flight booked in C from BKK-ZRH-LHR for my family of 4. I selected seats on both segments and the website shows the seat selection has been saved, but when I exit the seat selection window and return to the main my booking details page it only shows the saved seats for the ZRH-LHR leg. When I return to the seat selection page to select seats, the BKK-ZRH seats are open and the same thing happens when I try to select them.

I'm trying to select 9AB and 9DG since we will have a 4 yr old and 2 yr old and it shows that the seats should be selectable.