Check the file tags to make sure all the files have:
- Consistent sensible track and media numbers, meaning tracks 1-17, and disc 1 of 2 (or 1 of 4, or whatever)
- The same Album tag
- The same Album Artist tag (if it’s a compilation with more than one artist, this should be
Various Artists
)
If you find a compilation that’s not grouping properly, make the needed changes in your tags, and then rescan the files if the changes don’t get picked up automatically.