If you’ve ever tried to do a large group booking, over a certain number of people (I think 9, may be 8) cannot be booked online. This is the same with most, if not all, airlines. Once you lose that automation everything associated with that booking becomes harder.

At airports like MIA there are entire check in sections devoted to group bookings because of this issue. But they usually don’t have this many group bookings show up at once.

Still this isnt something they were surprised by. They should’ve brought in agents from elsewhere to help (they’ve done that in other situations).