I have a Roamio Plus with six tuners. Tuner 0 records most of my shows and every now and then they would not have sound. Sometimes there was no sound during playback while the show was still recording, then when recording finished, sound would be okay. Other shows had no sound after recording, deleted and restored, or rebooting. I think the issue is that something triggers the sound to switch sound track to #2 (Spanish in my case, which is silent). The fix is simple, when the sound quits, hit "I" (information), select "switch sound track", pick "English". Works for me.