This happened to me a few years ago and I needed to modify something with a text editor. The only thing that changed is I started pulling down the Plex member versions and not public releases of server. Dinked around with the settings under player and the same result.
When I try to play any movie in my Plex library to say a laptop, phone or Chromecase via plex the audio is horrible. Playing the video file using say VLC and it plays great.
