I tried adding three tracks to the end of disc 6 in http://musicbrainz.org/release/7c3bbce8-722a-42c6-a64c-c56a5286e949 , choosing "add a new recording" for the new tracks and not touching the others, but it fails with the given message.

When I try to use auto-editor privileges, I get a stack trace (attached) and the edit is not applied; when I did not choose auto-edit, the edit was entered into the queue, but it failed with the message given when I tried to approve it: http://musicbrainz.org/edit/15060789