I've encountered this as well, and I believe it's related to search head clustering as it only started happening after we upgraded to 6.3. Using |savedsearch was not an option for me, because it negates the primary effect of using |loadjob, namely, that I can schedule a long-running search to execute in the background and then pick up the results when my report or dashboard needs it.
I am able to use this as a workaround:
|loadjob [rest /services/saved/searches/mysearchname/history splunk_server=local |where isDone==1 |eventstats max(ttl) as maxttl |where ttl==maxttl |return $title]
Replace mysearchname with the name of your saved search.
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