Hello,
If you mean to "Use the automatic updater to automatically get the lastest version of DirectAdmin" in Administrator Settings, then I doubt it's working at all, unless I'm missing something. If you want to upgrade Directadmin with cron you should use custombuild functionality for this. If you would upgrade with cron only directadmin then it won't break your sites. If you are going to upgrade Apache, MySQL, PHP with cron then that someday might break your sites, which is rare, but still there is a possibility.