
Ari W. answered 04/12/19
Published Artist Teaching Graphic Design & Photography
Hard to do with Illustrator's built-in tools which will only report open paths but don't point to them. Try Astute Graphics' Vector First Aid plugin, it can pinpoint open paths and fix them along with numerous other problems. I believe they support older versions of AI including CS6. Also try the free Select Menu plugin from rj-graffix, which can help you select all open paths so you can fix them manually.