Just overheard an example of this when I was dealing with an agent. Woman to my right was complaining because 2 bookings she had were "There this morning". AC spontaneously cancelled one booking and then cancelled the remaining flight.
She was quite perturbed b/c this was "precisely why she made 2 bookings" she informed everyone in a 2 gate radius.
Further twist, it sounded like she booked a redundant second leg, given fragments of the conversation.