I have an updated version of 5.3.1 where no ACF fields can be edited anywhere on the site. I can’t even edit field groups. In editing screens the ACF fields just “spin”, here is the caught Syntax error that points to acf-input.min.js
Is this still a problem in the latest version of ACF?
If you’re still having an issue try deactivating other plugins to see what’s causing the JS error. Any error, either in JS or PHP can cause the AJAX request to fail and you’ll get the behavior you describe.