MediaMonkey’s auto-sync functionality normally syncs only one copy of a file to a device. Tracks may be unnecessarily re-synced if:

1. the timestamp of the file in MediaMonkey is more recent than that on the device. This can occur if:
   • The files have a future-dated filestamp.
   • The file server, PC running MediaMonkey for Windows, and the device being synced to have clocks set at different times. Setting them to matching times will resolve this.
2. the destination sync format is changed after syncing a set of files, causing the next auto-sync operation to have duplicates. The solution is to enable ‘Delete other files and playlists from the device’.
3. a non-standard destination sync format based on Playlist names is used. e.g. if a track appears in multiple playlists, a destination with the <Playlist> in the path will have multiple copies of a track.
4. manually syncing files can create duplicates of files that have previously been synced.
5. If a device has multiple storage locations (e.g. internal storage + SD Card), the sync profiles for each location are configured independently, so for example, it’s possible to accidentally choose the same Artist in both profiles, resulting in duplicates.