When using Prefer local metadata, you need to be absolutely certain that the embedded tags in your media files are accurate. If you have tracks in the Various Artists folder that have an embedded album artist tag that isn’t literally “Various Artists”, you’ll continue to stumble upon this issue.
Warning : If you have embedded metadata and particularly if you enable the Prefer local metadata setting for the music library, you need to make sure that the embedded metadata follows this information. Failure to do so can cause all the Various Artist content to be mis-categorized under a different artist.
You can use something like MusicBrainz Picard to clean up your media tags. Alternatively, you’re less likely to see this behaviour if you disable the Prefer local metadata setting.