Bug report,
Logging into windows causes my default speakers to always start as muted(but only system sounds), but then selecting the sound does not show source as muted. Work around seems to be to mute audio source, and then unmute to return to normal function.
Mine maintains the state that it was when I sign out or shutdown, if it was muted it comes back muted, if it was on it comes back on.
I saw one case on a Laptop that had a Realtek audio manager behaving strange in a similar way as you describe.