In season 1 - 3 of The Legend of Korra, Bumi's defining trait is that he won't shut up. When season 4 hits Bumi suddenly doesn't talk. He's in the background of shots and he even assists in a raid but he doesn't say a word. I'd understand a character just not having anything to do and having no reason to talk but Bumi is not only a habitual loudmouth but he's also a relatively active character in the last few episodes.
Did something happen there? Did his voice actor have conflicts or was the show unable to afford him due to budget cuts?