Why was Robin's VA replaced?

[Lazzie]

If this has already been addressed, then let me apologize in advance.

I noticed that Robin sounded a little strange in episodes 301 and 302, and then subsequently learned that Robin's original voice actress (Yuriko Yamaguchi) was replaced by a new one (Yuko Kobayashi) in episode 299. I know that Chopper's voice actress took maternity leave for awhile last year, but I haven't heard anything about why this new change happened. Can anyone enlighten me?

[warp]

Was she replaced in 301?! Wow I didn't even notice. I knew she was switched, but I haven't been watching the anime. So I watched 301 to see a difference and when Spandam and Robin were yelling on the bridge I didn't even notice. Wow.

[bevin]

Yeah, there's a thread about it already.