That could work, but I'm worried about the lack of a button in the volume slider. I haven't been able to reproduce this.
I'll be back online in a few hours, and I'll put some more thought into this. I can't see how it can be a hardware problem, but it might be.
In the meantime, why not play around with the lock orientation/mute settings.
If someone could guide you through a return to factory settings, that could be useful too, although I'd rather find out what has happened rather than hit it with the biggest hammer we have.
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