I have tried all the "troubleshooting" that I've seen on the Internet: reset the phone, reinstall iTunes, load without artwork, don't load MP3s, load only MP3s, don't use wireless, use wireless only, delete songs on iPhone first, don't delete the songs first, create a second set of songs and delete the first, transfer the songs one at a time, perform the transfers in album mode only, put a space in the Comments line, restart iTunes with the Shift key and have it re-find my library, etc. Have I missed any?
This is *not* troubleshooting, but simply grasping at straws. Legitimate troubleshooting is a backward step process where you have a piece of software architected properly that permits you to step into the process at certain points, or at least tells you what it was attempting to do when it failed - providing that it even *knows* that it has failed, which because these products are so poorly designed, the application usually doesn't even realize that it has not carried out the instructions that the user gave it.
This is why you see in these blogs someone post a "solution" and it will work for a few and it won't work for others (ref mgrassni in this thread). Then somebody posts a second solution. Then a third. Etc. Then when all else fails, Break Glass and Re-Install.
Apple has bragged that their stuff is not "buggy" like what we get from the Redmond Gang *because* it is a closed, carefully monitored system. So how could it be possible for users to be screwing things up on our own? I have a standard iPhone 7 with the latest release of iOS 10 on it. I have the latest release of iTunes on my Windows box (12.5.1). I haven't hacked or touched any of the Apple software or hardware. Windows' job is to only make sure that my iTunes sees my iPhone, which it does. It is syncing just fine. No, the issue is obviously between the two APPLE products, not my Windows box.
The upshot is this: unless we know precisely why a problem occurs, a random "try this" approach to fixing it is no solution. It only kicks the can down the road.