I think I know why. I can't seem to sit down for a perfect 8 minutes for each video due to many distractions (like a baby). So I have to pause the video and resume in the middle of several sessions, and I think that's what screws up the sound a bit. I guess it can't be helped. I can't really go back and perfect those videos unless I want to replay the entire game all over again, so you're unfortunately gonna have to deal with it.