So I made the silly mistake of trying Spotify Chat to address this. I disconnected when he told me to "reboot my router". Ugh
I've attached a PDF for you to play along at home. Let's say a year ago I "like" several tracks on Guns N Roses' album, Appetite For Destruction. There is only one version of it then, and also now.
These numbered points correlate to the slides in the PDF.
I'm looking at the auto-created "Your Top Songs 2020" and noticed tracks that I know I've liked before are showing not liked. In this case, "Think About You" was not Liked.
I go to my Liked Songs to check, and sure enough, it's marked as "Liked'.
I click on the album title from WITHIN my Liked Songs, and it shows me the album, with the same songs Liked, as expected.
So I start from scratch, search for Guns N Roses, look at their discography, and choose the only version of Appetite For Destruction shown.
Opening the official library album reveals that NONE of the tracks are marked as Liked.
So I believe this explains why I realize I haven't heard whichever song be played in my playlist for months/years. I feel like Spotify routinely removes and re-adds albums, whether it's because the artist re-uploaded, or a licensing change, whatever. But this doesn't have anything to do with a "remastered" or "deluxe" version getting added or swapped out.
This sucks for the customer, as my painstakingly curated Liked Songs list is often wrong, and songs get skipped over because they are not Liked in the internal Spotify library.
Every few months I have to go through the thousands of liked songs I have and randomly spot check things. I ALWAYS find songs that are Liked in my Liked Songs list, but not in the main catalog. It's frustrating.