I don't have much helpful to add, other than to confirm this issue is present in one of my environments too.
Log shows (trimmed):
05-14-2018 16:46:39.773 INFO SearchStatusEnforcer - sid:rt_1526334389.764 Search finalized.
05-14-2018 16:46:39.773 INFO SearchStatusEnforcer - sid:rt_1526334389.764 Search auto-finalized after disk usage limit (0MB) reached.
05-14-2018 16:46:39.773 INFO SearchStatusEnforcer - State changed to FINALIZING due to: Search auto-finalized after disk usage limit (0MB) reached.
05-14-2018 16:46:41.917 INFO DispatchManager - DispatchManager::dispatchHasFinished(id='rt_1526334389.764', username='admin')
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