Sound Issues - YouTube & Various Channels

We are consistently having issues with sound going out while streaming YouTube.  I mean, I don't mind sometimes because then I don't have to hear the [Edited: Language] my kids watch, but it is annoying and shouldn't happen.  It also happens on various other channels here & there.  To fix it, we have to either change the channel and come back, or when it's YouTube the kids have to rewind and then play again.  We've traded boxes and that didn't work.  We have no issues when watching Apple TV so I do not suspect it to be any other issue besides an Xfinity one.  I don't plan on unplugging the box or restarting anything anytime soon since this doesn't seem to be a personal problem.  I just want Xfinity to fix the issue.