Importing music returns `Enter a valid UUID`

I've got a large number of song files (2503 right now) that are returning the following error during import. For an example here's one album:

2487/2503 Importing /srv/funkwhale/data/music/Yes/The Yes Album/01 Yours Is No Disgrace.flac...
2488/2503 Importing /srv/funkwhale/data/music/Yes/The Yes Album/02 Clap (Original Album Recording).flac...
2489/2503 Importing /srv/funkwhale/data/music/Yes/The Yes Album/03 Starship Trooper.flac...
2490/2503 Importing /srv/funkwhale/data/music/Yes/The Yes Album/04 I've Seen All Good People.flac...
2491/2503 Importing /srv/funkwhale/data/music/Yes/The Yes Album/05 A Venture.flac...
2492/2503 Importing /srv/funkwhale/data/music/Yes/The Yes Album/06 Perpetual Change.flac...
2493/2503 Importing /srv/funkwhale/data/music/Yes/The Yes Album/07 Clap (Studio Version).flac...
2494/2503 Importing /srv/funkwhale/data/music/Yes/The Yes Album/08 A Venture (Extended Mix).flac...
- /srv/funkwhale/data/music/Yes/The Yes Album/01 Yours Is No Disgrace.flac: ValidationError ['Enter a valid UUID.']
- /srv/funkwhale/data/music/Yes/The Yes Album/02 Clap (Original Album Recording).flac: ValidationError ['Enter a valid UUID.']
- /srv/funkwhale/data/music/Yes/The Yes Album/03 Starship Trooper.flac: ValidationError ['Enter a valid UUID.']
- /srv/funkwhale/data/music/Yes/The Yes Album/04 I've Seen All Good People.flac: ValidationError ['Enter a valid UUID.']
- /srv/funkwhale/data/music/Yes/The Yes Album/05 A Venture.flac: ValidationError ['Enter a valid UUID.']
- /srv/funkwhale/data/music/Yes/The Yes Album/06 Perpetual Change.flac: ValidationError ['Enter a valid UUID.']
- /srv/funkwhale/data/music/Yes/The Yes Album/07 Clap (Studio Version).flac: ValidationError ['Enter a valid UUID.']
- /srv/funkwhale/data/music/Yes/The Yes Album/08 A Venture (Extended Mix).flac: ValidationError ['Enter a valid UUID.']

These files are then missing from the database, and a re-scan performs the exact same task and returns the same error again.

I've gone through the docs but don't see a specific cause of this mentioned there. I don't think it's a tag issue as these files were tagged by beets and I don't see any UUIDs in any other (working) files. This is from an in-place music library import since that might be relevant; /srv/funkwhale/data/music is a symlink to a network drive containing the files.

The exact command I'm using is:

${HOMEDIR}/virtualenv/bin/python ${HOMEDIR}/api/manage.py \
    import_files \
    "${MEDIADIR}/**/*.flac" \
    --recursive \
    --noinput \
    --in-place

Any suggestions appreciated (of course it's all my favourite albums doing this 😆)!