When I tried to send form_field_groups with my signature request, it would always throw this cryptic error: ``` {"error":{"error_msg":"'form_field_group' must have fields in 'form_fields_per_document'","error_path":"form_field_groups","error_name":"bad_request"}}) ``` I wrote to apisupport@hellosign (support ticket #19005626) and they pointed out that the request payload was not formatted correctly. I was passing this to `create_embedded_signature_request` ``` [ { group_id: "group_collections", group_label: "Collections", requirement: "require_1" }, { group_id: "group_insurance", group_label: "Insurance", requirement: "require_1" }, { group_id: "group_paymentplan", group_label: "PaymentPlan", requirement: "require_1" } ] ``` and this is how it was transformed to json ``` "form_field_groups": { "group_collections": [], "1": { "group_label": "C*** REDACTED [11 char]" }, "2": { "requirement": "require_1" }, "group_insurance": [], "4": { "group_label": "I*** REDACTED [9 char]" }, "5": { "requirement": "require_1" }, "group_paymentplan": [], "7": { "group_label": "P*** REDACTED [12 char]" }, "8": { "requirement": "require_1" } }, ``` My fix was to wrap the array in `MultiJson.dump(...)` because that's how the other fields were transformed (`prepare_signers` etc). I realize that this is a legacy issue and easy to work around, but I wanted to make it visible for other people who might be running into the same issue.