Cannot delete Indexing Verify/Rebuild tasks.

We have a few Indexing rebuild/verify tasks we are trying to remove. But everytime I try to remove these tasks, we get the message.

The subtask 'user' could not be stopped.

Reason: Task Controller service is not running on server

'server'.

The Indexing server for these tasks are not production servers. I moved the Indexing location to a different server as well, but still unable to remove the tasks.