The scheduled task zombie

17 December 2012
Recently I started getting errors in the Windows event log: 'Microsoft-Windows-TaskScheduler/Operational' Each time a particular task was running, I got two errors:
Event: 151 - Task Scheduler failed to instantiate task at service startup.
Task instantiation failed "Task Name". 
Check point: Load-CompareHash. Error Value: 2147750689.


Event ID: 101 - Task Start Failed
Task Scheduler failed to start "Task Name" task for user "computername\username". 
Additional Data: Error Value: 2147750689.

These errors started to appear after I changed the password of the user running that task. The task still did what it was suppose to do, but the errors annoyed me. I first reset the password again, then deleted and re-added the task, the problem persisted. During troubleshooting I managed to get rid of the errors and got a warning instead:

 Event ID: 322 - Task: Launch request ignored, instance already running
 Level: Warning
 Task Scheduler did not launch task "Task Name"  because instance "
73E2A202-35D9-4D81-AD8B-51B374A02DCE}"  of the same task is already running.

Which was not true and after re-adding the task I got the two errors back.

I then created a new task with a different name but using the exact same properties and the same user.

That task works without problems and throws no warnings or errors.

So I decided to give up on finding out where whose errors came from, I disabled the original tasks and was about to close the issue.

Well, guess what I am still getting the errors in the event log even though that task is no scheduled to run.

So I deleted the task completely to finally get rid of the errors.

Not so fast Sherlock! they still kept coming even though I could find any trace of the mentioned task on the machine anymore.

Nothing when using the GUI, schtasks.exe or in 'C:\Windows\System32\Tasks'

It refused to die and keep coming back to haunt me.

A reboot of the server finally put the task to rest.

This all happened on Windows Server 2012 core.

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