I have a Magnavox 25 inch and am having a problem controlling the sound. All the buttons on the television itself work fine but cannot control the sound with the remote control. Tried cleaning the sensor window with no luck, got any good ideas i can try. One more thing I can control the sound every once in a while with the remote but that's only for a few minutes then it stops responding. We tried different remotes with the same result - sound only responds sometimes.