IntegrityError: duplicate key value violates unique constraint "modelversion_unique_hash"

Steps to reproduce:

open https://arkindex.teklia.com/api/v1/model/<model_id>/versions/
create a new version with {"archive_hash": "<hexdigest>", "hash": "<hexdigest>", "size": <int>}
try to create another version with the same payload
backend returns a 500 with the integrity error

UniqueViolation: duplicate key value violates unique constraint "modelversion_unique_hash"
DETAIL:  Key (model_id, hash)=(53584817-12b0-4d71-a66e-d016781d97ba, 594f803b380a41396ed63dca39503551) already exists.
  File "django/db/backends/utils.py", line 105, in _execute
    return self.cursor.execute(sql, params)
  File "psycopg/cursor.py", line 97, in execute
    raise ex.with_traceback(None)

IntegrityError: duplicate key value violates unique constraint "modelversion_unique_hash"
DETAIL:  Key (model_id, hash)=(53584817-12b0-4d71-a66e-d016781d97ba, 594f803b380a41396ed63dca39503551) already exists.
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  File "arkindex/training/api.py", line 195, in create