API indefinite wait by aws webpagetest-server-2014-11-25 - ami-fcfd6194 (us east)

I’ve got an instance of ami-fcfd6194 running.

If I start it up, it takes API and web UI requests fine.

But spontaneously, eventually, it will stop responding to API requests. The response never changes from:

Waiting at the front of the queue..

If I make a web UI request, it the API responses change to:

Waiting behind 1 other test...

But then the web UI test finishes and the API responses go back to

Waiting at the front of the queue...

Indefinitely. If I stop the instance and start it up again, the API requests go through again.