Apple Music Album Artwork Inconsistency

My music library consists of local mp3 files. I don't have an Apple Music subscription and so am using the macOS app like iTunes as just my personal library of songs.

For individual tracks, I have started adding their "single" artwork to the individual songs. If the first song has a different album cover, it changes the entire album's look in my library and so I've just skipped those.

The albums all look how I want in Apple Music on macOS, but when they get added to my phone the cover artwork changes (seemingly randomly, I can't pinpoint what differentiates those anomalies).

It's not a huge deal (obviously) but if anyone has any ideas of how I could keep that consistent, please let me know, thank you.

Attached are images of two examples. One being Blake Mills "Jelly Road", correctly rendered on my computer, incorrect on my phone. The second being Vampire Weekend's "Contra", same situation.