Yes!! This is one the most atrocious debasements of character an author can commit!! Case & Point: The Kricket Series by Amy Bartol. Two books worth of excellent characterization, followed by a poor excuse of an ending! I don't want to hurt anyone's eyes or brains but read it as an education on what not to do!
I loved this because Arthur, when he and Merlin are alone together, always throws stuff at Merlin or teases him. But when Uther walked in it was like, "Oops! We were acting like two little boys and Daddy caught us." xD