I'm surprised that you retuned the Humax box. It's the only electronic device that I leave on standby overnight because it takes automatic updates. Did it ask to be retuned? I must have missed it. I retuned the Samsung TV.
The Humax box is an awkward little devil isn't it? One wrong button press on one of 3 remotes and all sorts of strange things happen. And don't get me going on subtitles that come up only on playback or sometimes it switches to analogue tv (blank screen) and it's always the ‘other’ remote that is the one with the digital/analogue switch.
I agree about sound level problems too. If only there was an overall control that could keep the sound levels even, no matter what the TV channel, whether the Humax is in use or not and whether or not adverts are playing. It's not just the Humax, together with the TV and sound system, they just don't play nicely together!