You may refer to this tutorial, it's about how to fix iTunes sync problem with iPod.
http://www.mac-dvd.com/how-to-fix-itunes-sync-problem-with-iphone-ipod-ipad.html
Please help! After several years of working without an issue, I tried to sync my music recently (the only changes were that I edited existing playlists, no new music was added or deleted.
The issue appeared as follows:
- Firstly I saw error 69. I removed all music that appeared to be an error (given that no songs had given this error beforehand, I don't understand why all of a sudden itunes wouldn't allow my ipod to sync with songs it had previously synced)
- Once I had removed these songs, I attempted again to sync, but itunes now just freezes mid sync (sometimes on a song, sometimes not). Sometimes itunes will sync a song, and sometimes it will freeze on that same song and state "error 69"
- I uninstalled and reinstalled itunes. The issue remained.
- I uninstalled and reinstalled my entire music library. The issue remained. I created new music libraries that do not have any songs from my previous music library. The issue remained.
- I have attempted to sync another ipod, which previously worked. It experiences the same issue now. Both ipods now, every time I attempt to sync, request me to restore defaults and scan and fix issues with the ipods. Sometimes I do so, but it makes no difference.
- In summary: itunes will not sync even if uninstalled and reinstalled. I have tried syncing two different ipods, both of which synced without issue previously, but neither will sync now. I have tried uninstalling, reinstalling and creating a new music library, but itunes still will not sync.

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