Python SDK batch create users 400 error

Trying to bulk create users from CSV using the Python SDK. The create call works fine one by one, but when I loop through the list it throws a 400 Bad Request on the second iteration. Here’s the snippet:

for row in users:
 user_req = UserRequest(name=row['name'], email=row['email'])
 users_api.post_users(user_request=user_req)

No specific error message in the response, just 400. Any ideas?