Yes this happened to me as well. As mentioned below the 'system' has your seat and the BP is more or less irrelevant. If you have the iPhone app (as I did) the seat updated to the correct one based on an equipment change (772 3 class to 772 4 class in my case). I think the bar code on the BP simply tells the system who you are and your booking ref, and the seat is updated as needed. The fact that is it written in ink on the BP does not really matter. So, is fine.