Comment 8 for bug 298301

This looks very much like a duplicate of bug #378470 and/or #432660. Please check that bug and mark this one as a duplicate if that is the case. (it would probably help to keep #378740 the "original" bug, since it already contains information about an (although unregarded) upstream bug)

Also, I found elsewhere that there were some other muting related problems fixed in pulseaudio 0.9.15, but from my understanding they describe a different bug. But you might want to try to recreate your bug with a newer version.