Stuck waiting on changes to be applied iTunes Win12.0.1.26
Have been adding music to my library. I now have about 12K tracks, and tried to sync to my iPhone 6 Plus 128GB. I am using 192Kbps default, as I feel at 128Kbps music is missing.
Every time I tried to sync, iTunes would begin, determine the tracks to be sync'ed, and then would become stuck "Waiting for changes to be applied...". It should have proceeded with converting and copying tracks to the phone.
Investigating my iPhone's (On My Device's) Music section, I see all tracks, greyed out. Only the items I purchased directly from iTunes are sync'ed, because the phone is set to automatically download them.
To make a long story short, I searched the web, tried Wi-Fi, tried clearing all music sync's, tried a different USB to Lightning cable, let it sit at the suspect prompt over-night, all to no avail. I even tried mounting the ITDB to a different computer; same results.
It appears to me to be a bug; In past, with about 6K tracks, I was able to sync with USB cable (but not Wi-Fi). So I cleared each item in the playlists I used to sync, applied, waited for it to finish, then cleared the Sync Music and applied again. Once done I checked Sync Music and Selected Items, and applied. I then started syncing a few playlists at a time, trying to keep the tracks under 2K. It appears to be working, at least with USB.
iPhone 6 Plus, iOS 8.1.1, 128GB