Errored Backup jobs not on client, but in Task list on management console

I have three jobs that are listed in the management console that encountered errors (backup server crashed while backups were processing). Yet these tasks are not found on the clients when I use schedmgr.exe and look for the task ID. It won't let me delete them from the "Tasks" list!

For example, there's a Validation task for workstation1 that is "Idle" with an error condition because it was running when the server crashed. I removed the policy from the workstation and redeployed it, so there is a new Validation task, but the old one is still lingering along with a Full Backup task for that workstation that also doesn't match any job on the client.

How can I clean these jobs out of the management console's list?