yeah I've noticed the same.. like usually i turn it off at night but then later the next day its a half way point again.. I just thought i was changing it in my pocket or something. Not really something I'm to worried about.
The problem is caused by phone app. Each and every time I make a call, then the media volume goes mute. I installed an app (volume fixer) from the play store but it's really frustrating to use the app every time after the call.
It's undoubtedly caused when making a call. Any permanent solution?