"Saving Music Libary" hangs, cannot complete, have to force quit

I have a large music library -- over 15,000 albums. For years I have struggled with the new Music app -- the iTunes replacement -- where it would hang, "forget" where 90% of my library was stored, and so on. I have reinstalled the OS countless times, rebuilt the library countless times, spent hours on the phone with Apple support -- you name, I did it. In the end, I was told that Apple could not support my 6 year old Macbook Pro and that the only solution was buying a new laptop. Which I eventually did -- through gritted teeth.

I re-imported all 15,000 albums, but hundreds of albums were added as duplicates while other albums were only partially re-imported. I have been going through the library in alphabetical order, deleting duplicate albums and re-importing missing tracks. I got through A-L no problem, saving the library after completing each letter. Yesterday it was M's turn. And instead of simply quitting, the "Saving Music Library" prompt appeared onscreen and did not go away. After waiting for an hour, I force quit, shut down the computer, restarted Music. This time, a "Loading Music Library' prompt appeared -- and did not go away. I had to force quit again, shut down the computer, restart the computer, and then start Music in Safe Mode. This time the library loaded, but none of the content I had added as part of my reconstruction of M was visible within the app. I checked to see if the music I had added had in fact been placed in my Music folder on my external hard drive -- all the files were there. I decided to re-import just the missing M files and save the library. The "Saving Music Library" prompt appeared onscreen and did not go away. I shut everything down, dealt with more "Loading Music Library" prompts, but then decided to re-import the M files album by album. (I thought maybe I was adding too much content at once.) I was able to re-import 2 successfully, but the third one (containing at most ten tracks) led to the "Saving Music Library" prompt appearing onscreen and not going away. And force quitting meant none of the new content for the third album I added was visible within the app.

My online research shows that this is not an isolated incident. Others have experienced the Never-ending Saving Music Library prompt. I have not seen a workable solution. Does anybody have a fix for this?