See the Amerigo Gazaway edit form for an example of the issue. I'm not sure what's wrong here, or how much it may also affect other types of link, but some part of the new link editor doesn't seem to be parsing and displaying the link data correctly, and leaves the form in an unsubmittable state due to validation errors.

This seems to have been produced by marking an existing SoundCloud link as 'ended' (edit #82567120) and then adding a new (and different) SoundCloud link (edit #82567121). The edit form (and the external links list on the view page) now only show the newer link, though both are presumably still in the database, and causing validation issues in the edit form.