You shot for sab shows that "Relative folders are based upon /mnt/user/appdata/...." This works because you've passed through /mnt to /mnt on sab
However, you didn't do that on Radarr, which means that radarr's error message will make it look like everything should be right, but since /mnt isn't mapped to /mnt on it's template, radarr won't have access to the files.