https://www.manageengine.com/products/eventlog/iis-server-auditing/iis-was-event-failed-to-send-application-unconfig-to-protocol-5151.html
5151: WAS event failed to send application unconfig to protocol
Event ID 5151 in IIS Web Site Availability is generated when Windows Process Activation Service does not send a request to a particular protocol to remove...
send applicationeventfailedprotocol