Twitch advertisements have a different sample rate which messes up audio and video for live stream archives. See #492 and #581 for more information. There are a few workarounds -

• Use a proxy to get an ad-free stream. Configure in Admin > Settings.
• Subscribe to the channel for an ad-free stream and use your Twitch token in Admin > Settings.
• Re-encode the audio after archive.
  • In Admin > Settings change the FFmpeg parameters to -c:v copy -c:a aac to re-encode.