Is there any quick fix available other than overlay of /libs/cq/gui/components/siteadmin/admin/publishwizard/references/references.jsp . Any documentation providing details on what all comes as references through ActivationReferenceSearchServlet would be helpful.
Can you share the exact snapshot of "undefined" item that is part of the response or share the response object of "undefined" item alone (Shared screenshot highlights the items that are displayed fine)
Also, do high level check on contents of the page. (Example : see if you have Experience or content fragments authored as part of the page.)