For a very specific seat and/or if only one person is reseated, I would think someone with admin access did something, either for a passenger in need or for a passenger with rank in AY. Because an automated reseat would trigger change-of-seat-email, right?

But the "equipment change" excuse I doubt that is truthful. I've heard it many times, even when obviously not true.

Either this is a standard explanation they are taught to say without even looking, or there is a bug or operating error that triggers a reset of the seating-system and it looks like a equipment change to the agents. My guess is both are right as this keeps on happening and they keep on blaming non-existent eq changes.