My iPhone 5s would not sync music. It would hang & either just sit there or finally cancel. I finally fixed it after trying all these steps from forums & blogs
1. Unchecked all music & synced - did not work
2. Reset & restored - did not sync
3. Put phone in recovery. I did this twice, 1st time I resorted from back up, 2nd time I set up as a new phone - did not sync either time.
4. Uninstalled & re-installed iTunes - did not sync.
5. Deleted all apps on phone & from iTunes - SYNC WORKED!
I ran a diagnostic that showed one if the kernels was not in the right place BUT I also saw that one of my apps was constantly crashing, which pointed to a bad app b/c the diagnostic showed my battery in perfect condition. The bad kernel pointed to bad software, which is why I put my phone in recovery. When that didn't work I tried uninstalling iTunes. But when that didn't work still I figured it had to be the app that was crashing. Sure enough, deleting all if them from my ph & iTunes worked. The sync was hanging on the app b/c it was corrupted.
After doing this you can go into the App Store on your phone, go to purchases & re-download your apps onto the phone, then they will sync again b/c the path is fixed.