How to purge internal queue

There appear to be a set of tasks that were triggered via API that keep getting re-queued in Matillion's internal queue. Selecting the jobs and choosing cancel or selecting an individual job and selecting "Cancel and continue" does not appear to do anything. As a result, the instance is becoming slow/unresponsive. I've stopped and started it a few times. Is there a way to clear the queue so these jobs stop getting re-added?