Music playlist doesn't fully sync

[chainprayer]

I have a friend that is syncing a specific music playlist to his iPhone. After updating to iOS 6 this folder doesn't fully sync. Only about half of the files sync over, even though there is plenty of space available. Has anybody had a similar experience?

 

[chainprayer]

My friend just tried a full restore of his iPhone and confirmed his iTunes settings, but still no luck. It seems to copy over only a few files a time per sync.