When I first turn on the box, first time in a day, the audio will work fine for an hour +, then it will suddenly shut off. The picture will remain, but no audio. If I shut the box off and then turn it back on, the audio will return, but for a shorter period of time, roughly 20 min or so. As I shut the power off and turn it back on, the length of time that the audio will stay on gets shorter and shorter until it will only stay on for a few minutes before it goes off again. Help me!