The structured-artifact editor saves only one set of values for nested form elements. For example, the sample form "contactInfo" has a nested form called "phoneNumber", and "phoneNumber" has three fields ("type", "number" and "contact"). There should be at least one and possibly many instances of "phoneNumber" in a "contactInfo" instance. But when two or more instances are added, only the inputs for the final instance are saved.
(Hint to self: The problem is in the way the nested form-elements are named).