Apple Music not saving bulk "Get Info" changes - MacBook Pro/Sequoia

Having dropped Apple Music subscription due to not using it as much as I had expected, have deleted the library and am in the process of adding in my own ripped CD collection.

All is fine, except for compilation albums.

Some compilation albums import split. For example, if I have a compilation album with 12 tracks on it, I see 12 separate "albums", split due to the artist and/or the lack of a Various Artists tag in the Album Artist box.

If I "select all" 12 songs and change the normally empty Album Artist box to "Various Artists" from the drop-down list and check the " Album is a compilation of songs by various artists" checkbox then click "Okay", the box disappears, but nothing changes. If I reopen the still selected 12 songs, my changes have reverted, or, more likely did not save.

Incidentally, when I make the changes, green ticks do appear.

However, if I make the same changes to each of the 12 songs one at a time, then click "Okay", the changes are saved. After I've done this to all 12 songs, I get the compilation album displaying correctly.

I've done batch changes before, successfully (I saw a window appear making the changes at speed), but only before I updated to Sequoia. Is this a Sequoia bug that might be fixed, or am I missing something obvious?

Any suggestions gratefully received and any I have not tried will be tested.

Thanks in advance.