Python SDK: 422 Error on Bulk User Creation from CSV

Parsing a CSV of 500 agents and trying to create them in Genesys Cloud using the Python SDK. The loop runs fine for the first 10 users, then hits a 422 Unprocessable Entity on the 11th. The error body says externalPresence is invalid, but the CSV values match the enum exactly. Am I missing a rate limit or is the SDK batching requests incorrectly? Here’s the snippet:

for row in csv_data:
 user = PureCloudUser(name=row['name'], email=row['email'], externalPresence=row['presence'])
 api_client.post_users_post(body=user)

Any ideas?