Python SDK bulk user creation throws 400 on specific rows

Running a script to bulk create users from a CSV using the Python SDK. The loop works for the first 10 rows but crashes with a 400 Bad Request on row 11. Here is the snippet: api_instance.create_user(body=user_body). The error response says field 'division_id' is required but I am setting it in the JSON payload. Any idea why it fails only after the first batch?