I get this also, but only for a secondary USB sound device.
I have 2 volume-applets, the first works fine, the other spontaneously mutes
one channel, refuses to lock l/r, etc.
the mixer that functions is for a "HDA Intel"
the broken one is for a "Sound Blaster MP3+"
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Volume Applet still alter
I actually did observe this a few days ago in pavucontrol (one channel
moving spurriously, sudden muting while adjusting volume w/ mouswheel,
only on control for affected soundcard (the soundblaster mp3+ usb)) but
seems fine now...
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Erratic volume control behaviour with different USB audio devi
