Yes, I tested it in Dub Mode as well. I made a new recording there and playback is also completely silent inside the game.
So playback is silent in both the Mic Test & Crust page and Dub Mode. However, the recording files themselves definitely contain audio — I can open the saved recording outside the game and hear my voice normally.
Live Microphone also works normally.
So it seems like the recordings are being created correctly, but Choicer Voicer isn't playing them back correctly in-game.