Fixed in Vuo version:
Steps causing the bug to occur:
I installed macOS 10.12 GM and noticed that when selecting the Built-in Output in the French localization on the OS, there's no audio going out of Vuo. In French, the Built-in Output is called Sortie intégrée and Vuo replaces the accented characters with a "?" symbol. In OS 10.11, it was the same, but it didn't prevent the audio from going out of Vuo.
When I switch the OS to English localization and select Built-in Output in Vuo, the audio can be heard. If I switch back the OS to French and then in Vuo leave the audio output to Built-in (as it was saved when the OS was in English), audio is going out of Vuo. But if I switch from Built-in Output to Sortie intégrée, there's no more audio.
Maybe it's not strictly related to the accented characters, but it seems clearly related to the OS localization automatic renaming of the Built-In Output.