What causes this scheduler failure? "Error in 'summaryindex' command: Permission denied to index 'summary'."?

[twinspop]

06-08-2016 21:11:02.773 -0400 ERROR SavedSplunker - savedsearch_id="UserX;search;ss_index_delay_times", message="Error in 'summaryindex' command: Permission denied to index 'summary'.". No actions executed

The search is owned by UserX, and scheduled to run as 'owner'. UserX has plenty other searches that are running and saving to this same summary index. This very search runs perfectly fine most of the time. UserX is admin level.

It's running on a solo search head talking to 3 indexers. Index summary is defined on the SH, but the SH is set to forward to the indexers. No local indexing. Linux, running 64-bit 6.4.1.

[haliakbar_splun]

Can you confirm that the summary search is running is using the # enable summary indexing
action.summary_index = 1 or is the search using the search collect command? Can you paste the search if possible?

[twinspop]

Confirmed, yes. The box is checked.

A sample search, very simple:

error | stats count by host

but it hasn't happened since June 10th, a day we pruned lots of the per minute searches we had. Could it be related to overrun quotas? If so, strange message.