Comment 2 for bug 259566

I got the same problem, after looking in the code it seems that it's related to portaudio alsa host api "interfacing" who don't handle subdevices properly.
Your fix sadly didn't worked for me i got a choppy sound when trying to use the routed interfaces. So i will stick back to xwax for a bit, perhaps trying to fix portaudio alsa for that if i got the time.