Make sure the album artist is identical in all tracks of all the affected albums (case sensitive, no extra spaces or invisible characters, etc.).
I’m pretty sure the compilation flag has nothing to do with classifying ‘Various Artist’ albums.
Is the library configured to “Prefer local metadata?” There are some things to know in this case.
If all else fails, you can always select all these ‘Various Artist’ artists and merge them, but that might not be a permanent fix.
