Help with 'missing' plugin and negative counts

I’m doing something wrong with the missing plugin and I cannot figure out what. Specifically, for every album in my library, the value of $missing and the number of tracks for that album in the library are the same distance away from zero - that is, for example, if an album has 7 tracks, $missing == -7 This is true for every album in my library - including albums that I know I’m missing tracks from.
I can reimport an album with a missing track, beets recognizes the track as missing at import time, and yet the missing field still == -1 * total track count for the album.

here’s my complete config.yaml:

directory: /nfs/media/music
library: ~/.config/beets/beets.db
id3v23: yes
original_date: yes
format_item: $artist - $album - $track - $title
format_album: $albumartist - $original_year - $album
    copy: yes
    default: %lower{$format}/$albumartist/$album%aunique{}/$track - $title
    singleton: %lower{$format}/Non-Album/$artist/$title
    comp: %lower{$format}/Compilations/$album%aunique{}/$track - $title
plugins: convert duplicates edit embedart fetchart ftintitle hook info lyrics missing random scrub zero
    command: /home/davek/bin/ $source $dest
    extension: mp3
    copy_album_art: yes
    dest: /System/Volumes/Data/nfs/media/music/transcode
    album_art_maxwidth: 600
    never_convert_lossy_files: yes
    embed: yes
    itemfields: track title albumartist artist album year
    albumfields: album albumartist year original_year
    ifempty: yes
    maxwidth: 600
    cautious: true
    cover_names: cover front folder album
    minwidth: 300
    - event: item_imported
      command: echo "importing \"{item.path}\""
    - event: write
      command: echo "writing to {path}"
  fallback: ''
  source: musixmatch lyricwiki
    format: $albumartist - $album - $track - $title
    count: no
    total: no
    keep_fields: title artist albumartist album year track disc comp lyrics images
    albumartist: ['Various Artists']
    update_database: true

Anyone have any ideas?