Leviathan volume in browser occasionally extremely quiet

Occasionally, audio that is being sent from my browser through the optical port to my Leviathan is extremely quiet. When this happens, the only way to get it to be audible again is to unplug/replug it (sometimes works) or to do the factory reset by holding the mute button for 10 seconds (works when unplugging/replugging fails). It only affects audio from the browser, not from other programs. Chrome and Firefox (both up to date). Been happening on and off for a couple of months, but becoming more persistent.