iPhone showing random album art for imported music

First off, I still purchase all of my music and manually import/manage in iTunes (Mac), then transfer to my iPhone. I just recently added a few hundred new songs. Before importing them into iTunes, I added album artwork for all of them (all artwork <10MB). When I view them in iTunes on my Mac, the correct artwork shows up.

However, after transferring to my iPhone, many of the albums show random artwork from elsewhere in my catalogue. For one example (of many): Awaken I Am's "Blind Love" shows the artwork for Anberlin's "Lowborn". Again, in iTunes on my Mac, it shows the correct artwork.

This is how I have always managed my music and I have followed the same process for thousands of songs. Any idea why it's showing the wrong artwork for certain albums all of a sudden? I've tried deleting/re-adding the albums to my iPhone but it didn't fix it.

I have wondered whether there is a resolution limit above which the iPhone can't process tagged album art, but I'm not sure. I know it has trouble over 10MB but I always make sure all artwork files are <10MB, so that's not it.

Any help is appreciated. Apple already makes manually managing music hard enough without randomly replacing half of my album artwork.

Thanks in advance.