Thanks for the note here. I haven't heard of this issue. Have you tried removing the channel from the Roku home screen, restarting your device, then adding the channel back again?
If that doesn't do the trick and you're still running into this behavior, feel free to PM me with specifics including:
- The channel you were watching (and the specific TV station that this occurred on), including the date/time.
- The specific commercial/ad that appeared to be missing voice audio
- Your player model details, including the ESN from Settings>System>About.
With more info, I can help pass along your report to the channel publisher.
We'd also recommend contacting YouTubeTV support to report the issue within their channel and share details so they can investigate as well.