Not sure how this happened or how to fix it. I set up my 64gb iPhone 6 with about 6,000 songs. During a sync this morning, for no discernible reason it removed all but about 600 of them. This alone is frustrating enough but with every attempted sync I get stuck in "Waiting for changes to be applied" loops. Since then, the iTunes break down of Audio, Apps, etc. still shows the same total amount of space used but it has allocated 21.35 GB to "Other" and none of my attempts to fix it have worked. Note: in Usage, I see 3.1 gb in Music (some has been re-added in a new sync) and 1.7 gb in photos. Every other app has much less data listed. What I've tried: In Settings I tried to remove all music. It crashed Settings each time, even after a reboot. I manually removed all music, artist by artist, until empty then in iTunes unchecked Music and any related options then synced. It removed all the Music but Other was unaffected. Next I tried to restore a backup, but my encrypted Cloud backup doesn't show. Not knowing what to do about that, I backed up to my Mac expecting it wouldn't fix the issue because the problem would probably be backed up. I was right. The restore didn't fix it. Best I can think of now is doing a complete reset but getting the whole device set up from scratch is a daunting waste of time. I could restore my iPod's backup, which is how I originally set it up the other day, but that too will require many changes. I'm hoping someone else has a better, less draconian measure.