Incomplete copy of music from iTunes to iPhone

So I'm managing my music on my iPhone 6 (iOS 11) from my MacPro (OS X 10.12.6) using iTunes 12.6.2.20

and I keep getting an incomplete copy of music when I'm directly connected with my USB lightening cable (OEM Apple)

I can wait this out but it will never finish, and the songs that time out will copy over indivudually or in another set of drag and drops that will exclude anything else. Plenty of space on this phone too.