I'm not a product expert but I've done a bit of tidying up and moved your thread into the HIPs area. Hopefully someone can help you soon.
You may want to open a support ticket and request HF533861.
Issue: System startup or shutdown takes an exceedingly long time with Host IPS installed. (Reference: 533861, 537762, 540714)
Resolution: Host IPS could cause a thread from an injected process to wait unnecessarily. The process injection mechanism has been updated to remove the possibility of this wait time.