iTunes on iPhones showing wrong album art

I was finally able to get all the music tracks I wanted synced from iTunes on my PC to my iPhone (I have iPhone 6s by the way and the latest versions of my iOS, iTunes, and Windows 10). But one of the albums has the wrong album cover art. After searching online, the main suggestion I found was removing the whole music library from my iPhone and resyncing again, which should fix the problem. I attempted this three or four times, and it did not fix my problem--though one time it switched which album had the wrong art. Another time I went into my iPhone's settings and manually deleted all the music and then resynced--same result. (Note that the album art always looks perfectly accurate on my PC--just not on my iPhone.)

Also, every time I did the transfer, I received an error message about iPhone cannot be synced (error -54). Despite this, the tracks synced, just that a handful of tracks have the wrong album art each time.

How on earth do I fix this? I'm obsessive about how my music looks, so I can't just let this sit. Also, because it's a particular type of music, I actually created my own icons to serve as the album art, so it's not something that can be downloaded from any official sources. (I know some recommendations say to download the official art from iTunes, which is out of the question for me.)