Iphone + Music issue - need to sync twice to add music

I have had the same issue for quite some time - I wish I had an answer. Generally, syncing my music library with the phone is so much more difficult than it has any right to be, seeing as it is the one core feature that was the impetus for the first iPods that gave way to the iPhone. My iPad Pro syncs right up, but my iPhone has to be synced twice every single time, if it works at all. For months it would hang indefinitely on "Preparing to sync" and I would have top put it in airplane mode or perform some other voodooo to get it to sync. That problem went away only to be replaced by this issue. Also, randomly some things just won't sync or re-sync (if I change any artwork or song info usually). The sync will also fail if too many songs are being added... but in the world of streaming services this only effects the few of us who are music enthusiasts that don't rely solely on Spotify or Apple Music. TBH, I think there must be something either corrupt in my iPhone database file system or I have a bad memory byte or bit somewhere... but I have updated and started from scratch, only to get to the same place after countless hours of wasted time.

The only workaround I had was to sign out completely and back in (a reboot sometimes) and it works once. If I want to sync, even a few minutes later, I have to sign off again. It all started with the latest Mac OS update.