Troubleshoot specific query - why was it queued by Looker?

[DataChico]

We are trying to troubleshoot an issue where a query is executed in Looker and shows up as ‘running’ in the query page yet it has not even been sent to redshift. The query in question has been identified by the history_id and it shows that it took 400 seconds to execute according to Looker’s system reports yet only 5 seconds to execute in Redshift (0 seconds queued). 

Is there a way to determine if a specific query (based on history_id) was queued by Looker - and if so, why was it queued? Also, why would it show up as ‘running’ in the queries page - is this a potential bug?

From this article, it looks like these are some reasons that a query could be queued:

Per-User Query Limit and Timeout

Each Looker user is allowed to run 15 queries simultaneously by default. Any extra queries are queued in Looker until one of the 15 running queries finishes. If they stay in queue for over 600 seconds, then Looker drops them from the queue.

Scheduler Query Limit and Timeout

Scheduled queries are run by the scheduler as a given user. Thus, they are subject to the connection rules above, and the per-user rules. In addition, there is a scheduler concurrent query limit of 10 and a timeout of 1200 seconds.

Renderer Query Limit and Timeout

The PDF dashboard renderer process has a job limit of two. If a job times out, you'll see a RendererTimeout error message in the Admin Schedule History page. If you receive this error, please notify Looker Support and provide as much detail as possible.

For the case outlined above, none of these queueing scenarios would apply. Any thoughts on general query troubleshooting / mysterious queuing behavior?