Just a guess but I suggest you strictly follow the naming guidelines posted in the support articles, especially if you prefer local metadata, plus that you plex dance a couple of the non working albums after you rename them as follows.
If you have a music library that points to
Music/
then according to the naming guidelines all albums with various artists belong in a directory called Various Artists. So you should have
Music/Various Artists/
and under that you should have all your compilation albums, e.g.
Music/Various Artists/Guys And Dolls/
Music/Various Artists/The Rage of 1710/
Music/Various Artists/Guardians of the Galaxy Awesome Mix, Vol. 1/
Music/Various Artists/The Great Romantic Classics Vol.4/
and under each of directories you are strongly encouraged to name the tracks per the specification, e.g.
Music/Various Artists/The Rage of 1710/
01 - Rondeau from Sinfonies De Fanfares.m4a
02 - Canon for 3 Violins & Continuo.m4a
03 - The Four Seasons 3rd movement from "Autumn".m4a
You asked why it worked before but not always. Good question, but it’s better to start off by following the current naming convention exactly to eliminate variables rather than debug code none of us can access.
It takes a long time to build the perfect library, but doing that for a few albums as a test won’t be too hard.
nib
