Hi,
Windows Task Scheduler will by default run tasks at a "Below Normal" priority. You can check this in Task Manager. This can cause performance issues. To reset the priority you need to highlight your task and then then right click and export. Edit the XML field for priority and change from 7 (Below Normal) to 6 (Normal). Delete the Task and then import. If you now run you should see the task running as Normal in Task Manager.
I've not found any way to configure this in the Task Scheduler GUI so it is a slightly clunky procedure.
If this doesn't resolve the issue then I would suggest raising a Support Case.
Regards
David