The impacted custom fields/subfields do not have a default values configured
All required fields have to have a default value configured.
This extra validation was changed to address the CVE-2023-34063 vulnerability.
Resolution
Please export and retain any custom forms edited
Validate if all mandatory fields (Constraints: Required = yes) in the custom form have the default value configured and retry the request.
Where a default value has been added, you may need to change the Regular Expression to Conditional value with the condition being: if its dependent value is "Not empty"