that usually happens when an InformationObject is missing the slug or the publication status in the database. To fix the slug you could use a command line task from the AtoM folder:
php symfony propel:generate-slugs
To fix the publication status you'll need access to the database. If the following query doesn't return any result:
SELECT * FROM status WHERE object_id=217945 AND type_id=158;
You can add the publication status using this one:
INSERT INTO status (object_id, type_id, status_id, id, serial_number) VALUES ('217945', '158', '159', NULL, '0');
In the third value, use 159 for draft or 160 for published.
I hope that allows you to rebuild the search index without problem.
Regards.