Hey I'm having the same problem, with an additional problem (I found a work around, see at the bottom). This is not erratic device behavior, this is iTunes being a buggy product. (in my opinion)
I couldn't change any of the settings on my music files while on my phone (Side question: why can't I modify/delete files from my phone using iTunes? My best guess is the file was originally put on there using a different computer, not sure). I also can't delete the song from my phone using iTunes. This is not music from iTunes. I refuse to sync (it's very annoying and a pain when you want things a specific way) and I DEFINITELY refuse to restore my phone (it REALLY ***** when iTunes decides your backup file is corrupt, then you have to start from scratch trying to remember all the apps you had downloaded) (the problem is not my phone, it's either iTunes OR the problem is iTunes can't talk to my phone correctly, still iTunes fault). So, I deleted the file on my phone using my phone.
Now I want the music file back on my phone (with the new info/settings), but nothing happens!! it won't transfer over. I assume it is because iTunes thinks the song is already on there. AAAUUGGGGHHH.... very annoying...
Workaround:
I have to physically change the name of the song on iTunes before I can transfer it to my phone. That's just ridiculous. Please fix this problem.
Using iTunes 12.7.0.166 (newest update) on a Microsoft Surface Book
iPhone 5 - iOS 10.3 (is this a known issue with 10.3?)