I'm not sure if it's something on my end, but for a week or so, the audio level will sometimes reset itself to 1 when watching Youtube videos on Firefox. I was unable to identify any cause or pattern and couldn't find a way to reproduce it.
Unrelated and as a sidenote, but why is it no longer possible to use the mousewheel / arrow keys to adjust the volume level without explicitly clicking on it? It used to be possible to simply click on the addon icon and then adjust the gain with the mousewheel / arrow keys. The mousewheel does not seem to work at all anymore. I'd really appreciate it if this was possible again.