I've been saying it for a while now, but I'll reiterate and now with pics of EXACTLY why I said iOS software quality has gone severely downhill since TC took over. This may be my last dance with Apple unless there is a QC turn around at Apple. I'm afraid they STILL don't see the issues they are having or flat out ignoring them. Case in point: Every time I sync my iPhone (which I only do to load new music), I get missing album artwork EVERY TIME. Granted, my iTunes is LARGE and have all 16k tracks fit on my 128GB iPhone at 128kbps: My fix is to simply reboot the phone, which is obviously a huge time waster. Then all my artwork is back, but only after: Yep, it's resyncing half my library!!! causing even more time wasted. I mean Apple has only been syncing this way since the iPod. The funny thing is, it's been this way for me since iOS 7. That's right. I've had every iPhone, every OS, every version of iTunes, and yet I have the same persistent problem. It's obvious TC doesn't care about "it just works". I miss the old Apple really. I'm not saying they didn't have issues before, but it's never been this bad.
I sync 13GB of music on my iPhone 6+ and don't have this problem. In fact I re-synced my entire library a couple of days ago after I replaced the hard drive in my Macbook and did not see any issues.
Not sure what to tell you. Mine is working fine. So the iPhone 4 antenna problem under Steve Jobs was Steve's fault?
I have the same problem, with a 45gb music library. Each sync results in random albums losing their artwork, and no amount of reboots bring it back. I now just manage my iPhone as the primary source of my music, not the Mac. No more syncing!