The only similar thing I can think of is that the workflow is set to run as part of a chained analytic app. Each of the apps in a chained app is set to time out after 30 seconds, except for the last one. Check the workflow config
If it's not this, then similar posts suggest reaching to email@example.com so that they can take a detailed look at your configuration.
Hello, were you able to find resolution regarding this error?
I am experiencing the same error but it occurs when the Gallery is executing a scheduled job. The runtime is also 31 seconds and the mongoDB stores the same error message - "AlteryxProcessManager::Start: User Canceled". The Gallery returns an error of "There was an unknown error executing the application. The engine reported status Error"
The workflow is not a chained app. It runs often without error. The error appears randomly every few days.
I have searched all relevant logs and nothing appears abnormal other than this event.