If you’re getting the 404 on the feedback same as me, my problem was a rewrite rule that I’d put into htaccess to force a trailing slash on all URLs. This was forcing the trailing slash on the wp-json feedback URL as well, making it invalid.
Check that in the browser console. Sounds like a different problem if some forms are working though, so you’re probably best starting your own support thread.
After doing some more testing, it seems I’ve solved this. It was a url rewrite issue in the site htaccess.
