We have a new Vizio Smart TV, a Panasonic blue ray player, A VCR, a stereo receiver, and Xfinity Cable Box. The sound works fine on TV and VCR. However, sometimes when we put a DVD in our player, we get video but no sound. It's weird too, because if we hit the first notch of fast forward, we will get sound - speeded up a bit, but on regular play, no sound. We thought it was our DVD discs at fault, but there must be something else going on. Any help?