I have the exact same problem. This needs an urgent fix.
First time if i submit form it only shows orange blank box, no message inside.
https://#####/wp-json/contact-form-7/v1/contact-forms/17778/feedback?_locale=user
{“into”:”#wpcf7-f17778-p17770-o1″,”status”:”validation_failed”,”message”:”One or more fields have an error. Please check and try again.”,”posted_data_hash”:””,”invalid_fields”:[{“into”:”span.wpcf7-form-control-wrap.signature”,”message”:”The field is required.”,”idref”:null,”error_id”:”wpcf7-f17778-p17770-o1-ve-signature”}]}
Second time if i submit after error without changing anything
{“into”:”#wpcf7-f17778-p17770-o1″,”status”:”mail_sent”,”message”:”Thank you for your message. It has been sent.”,”posted_data_hash”:”cb6f253f437f3132c105e30aa5e8677d”}
and plseaes find all details here.
https://json-parser.com/42175710
or
https://jsoneditoronline.org/#left=cloud.d6a980c98e5142e0bfcea25d54e462e8