Ok.  My eyes are not working correctly at the moment.    

Misread that it 'didn't happen' again.

On mine, when this problem occurred, the display showed the volume bar going up.  Mine also did it with J205 unplugged.

Mine occurred due to batt damage on the CPU board.

If you are able to take a photo of the batteries on the board - close up and clear (macro shot) just to eliminate this otherwise I'm out of ideas.