We get this issue occassionally but only on one channel for some strange reason (320 if memory serves right), we just change channel momentarily and then go back to it and everything works OK until the next time.
Which box have you got ? I'm using the UHD box connect to a home cinema amp and have not had such issues.
It does occaisionally go funny ( the narration comes from the side speakers) after skipping advert breaks but if I pause/play it solves it. ( It's always done this I think)