Recently hooked up a Roku TV to my Xfinity/Comcast cable box, and the sound often goes out when I'm watching cable. It can happen when I first turn the TV on or when I hit the mute button or even just changing channels. No sound from cable. The audio on all the Roku apps work fine, and I have to "reset" the cable sound by turning off the cable box, going to a Roku app where the sound is working, then going back to cable and turning the box back on. This fixes the problem, but it's becoming a major headache. Never had an issue with the cable sound prior to installing the Roku TV. Any ideas?