Palmie said
It seems that my last Fetish Authour has very bad sound. The original doesn't have the greatest sound, but it's not this bad. I had to split the file myself because it was too big. I tried to fix it by doing it all over again, but this didn't help. Any ideas? 
  

You can use ffprobe to get the video details of the videos that have issues, and post the output to GPT. It is pretty good at giving you what you need to do / fix.