When experiencing large delays of IIS calls in IIS logs, and PST Flight Deck is having problems with communication between modules, check the Binding settings in Internet Information Services Manager (IIS).
By default, there should be only one binding in Default Web Site in IIS as on the following screenshot:
To access this setting, simply right-click on Default Web Site and choose “Edit Bindings”:
This is the setup that can cause issues in IIS communication:
By deleting all the bindings and restarting the service, IIS should resume normally.