This will occur if your audio file is corrupt or becomes corrupt during transfer.
Corrupt Source Files
Although unlikely, if you never checked your audio file before uploading, the source file itself could be corrupt. Be sure to try playing the audio files on your computer before uploading them to the server to ensure they play smoothly. If they do not, please re-encode them from their source, confirm it plays successfully on your computer and finally upload the file by FTP for AutoDJ to play as normal.
Corruption During Transfer
If the source files sound fine on your computer, but are distorted beyond recognition when they are played back through AutoDJ, they were likely corrupted during transfer to the server. Check your FTP application's settings to ensure the Transfer mode is set to Binary. Although rare, sometimes FTP applications will detect your media files as text rather than music and attempt to upload them in ASCII mode. Forcing it to transfer the files in Binary mode will resolve this problem. In Filezilla, you can force Binary mode transfers by going to the Transfer menu then choosing Transfer type > Binary. Check out this helpful video to see how this is done.
Once your FTP application is configured to transfer your music in binary mode, you will need to re-upload the audio files you already transferred, overwriting the server-side copy with the now exact duplicate.