Copying songs manually results in albums getting split up

I'll copy songs from my Mac to iTunes and transfer them across to my phone, everything transfers fine. However, when I view my library on my iPhone by either artists or album, some entries will split every track on an album into individual albums (i.e. Toto IV by Toto has a separate entry in the albums list, one for each track). It happens the most when using automatic sync or autofill. Then I have to go and delete every album that is appearing split up and re-copy manually by drag-and-drop, and EVEN THEN it still sometimes splits them up.

There's no rhyme or reason. Happens to all file types, all ID3 tag types, artwork or no artwork, long or short albums, it's just a mess.

This has been going on for as long as I can remember across multiple versions of iOS and macOS, and it's absolutely infuriating for someone like me who has a carefully-curated library of imported CDs. It makes me want my iPod Classic fixed because that never had problems, but the iOS music app is a disaster for locally stored music. I get that Apple wants us to use Apple Music, but come on.