Custom lyrics not showing on Music on ios 13 on iPhone

TLDR: Songs in .mp4 with custom self-inputted lyrics on iTunes not showing on Music ios 13, despite custom lyrics being visible on ios 12.

I have on my iTunes (on Windows 10) songs that I have imported in mp4 and mp3 with custom lyrics that I self-inputted. When I sync my iTunes stuff onto my iPhone (SE 2nd Generation on ios 13.4), those custom lyrics are missing (lyrics button is grayed out) despite being present on iTunes. Moreover, I noticed that only mp3 (audio) files have retained the custom lyrics from iTunes but mp4 (video) files have not. I have noticed that when I modify the custom lyrics of a song (mp4) on iTunes and resync to my iPhone there is an indication that the song has been modified on the syncing bar on iTunes and it shows that it is resyncing the song despite the custom lyrics not showing on the iPhone.

When I sync to my older iPhone 6 (which I think is ios 12), the custom lyrics are showing normally for songs (mp4 & mp3). I do not have an Apple Music subscription.

Things I have tried (but didn't work):

• Unsyncing everything then resyncing everything
• Restarting iTunes, computer, and iPhone
• Modifying custom lyrics on a song and resyncing

Looking if anyone has a solution for this problem.