I've had a TiVo Premier for a year with no problems. But recently it started having the audio dropout problem on playback that many others have posted about for years, over many different TiVo models. You can do the 8-sec rewind and hear the audio correctly so it's not a problem with recording.
The threads I saw seemed to suggest the problem was either Dolby output or a failing HD. I switched the output to PCM but the problem remains. I haven't tried replacing the HD yet; have others done this, and does it fix the audio dropouts? The only other thing I've tried so far is restarting the TiVo but that didn't do anything.
Edit1: I removed power, waited a few seconds, and plugged it back in. Now playback audio is ok. BTW the audio dropout seemed to be on all recordings.