I'm having a weird problem which is somewhat similar to the OP. Workflow:
Surface Book #1: Vinyl Studio => FLAC (local hard disk), Saved Tracks moved to a NAS drive.
Surface Book #1: JRiver Media Center FLAC (pointing to NAS) => MP3 conversion (saved to USB hard drive).
Unplug USB hard drive.
Surface Book #2: The USB hard drive is the iTunes library. Boot up iTunes, plug in iPhone. Add new folders to iTunes music library. Drag files to iPhone to force sync (iTunes is set up to do a manual sync).
This is highly similar to the workflow for CD rips except it doesn't involve Vinyl Studio obviously.
When I look at the song files in iTunes on Surface Book #2, everything looks fine. If I open explorer in Windows, the metadata looks fine. If I look at the tracks in the Music app on the iPhone, the album art is correct, the album title is correct but when I click on the album, the track listings all say "Vinyl" for the title and the album says "Vinyl by Unknown". This is clearly some artifact of VS (the CD workflow does not have this problem). Even more weird, when I start playing an individual track, the title, album artist, etc. is correct! I can provide shots of the phone in case this helps.
Why is this happening and what am I doing wrong? I'm trying to get tracks to my phone for a long road trip and am at a dead stand still on the phone ingestion side of things. Thanks for the help.