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If you reformat those to "cf:location" and "cf:employeetype" it should resolve the issue and populate the custom fields correctly for the contacts you are adding.
When you call GET /contact_custom_fields, you’ll notice it returns the value for the property "label” as the custom field appears in the UI, but the property for "name" returns a value that has removed any uppercase letters and replaced spaces with underscores.
GET custom_fields Collection
Please have a look and let us know if you have any other questions!
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