Song from my personal owned album deletes from album if I star it

I have 400+ albums that I own the CDs for, and which I long ago imported into my Apple iTunes library. Over the years, Apple has replaced all my actual music data with their version of the same thing (skipping a few albums they didn't have). That wasn't exactly what I wanted, but whatever.

Just tonight, I'm listening to my Iron Maiden: No Prayer for the Dying album (not one of the several remasters in the Apple Music streaming library). I starred one of the songs, and after a couple of seconds it stopped playing that song and jumped to the next. I tried to go back, and I discovered that the track was now gone from the album. 1,2,3,4,5,6,7,9,10. Track 8 (Hooks In You) is now gone. I can't find it anywhere now in my library.

To be sure I hadn't made some mistake, I starred track 10 (Mother Russia) as a test. Sure enough, it then vanished from the album and is now gone from my library.

I am not currently subscribed to Apple Music, but I should not need to be to listen to my owned music.

Also, I should node that I am not able to use any other MP3 player to play my music library since Apple disallows file access (meaning other MP3 players can't just read my personal MP3 files out of a folder on iCloud or the iPhone local storage).