So a quick update - this was resolved and many thanks to @bobbyD for helping fix it.
If anyone else has a similar issue, you can delete the stuck scheduler job by browsing to the following and then rebooting the hub.
http://your-hub-IP/hub/advanced/deleteAppJobs/302
Replace the 302 with the Job ID of the stuck job. In my case if you see this thread you can see it was app302.
In terms of identifying this, see the Hub events, and if you see a schedulerError, then in the logs, filter on error and see which one is stuck - use that JobID. However before navigating to this deleteAppJobs endpoint, make sure you delete the app and then go about this.
Thank you @mrvjtod for your guidance as well!
