Typically AWS load balancers aren’t static IPs. Amazon scales the LB up/down or rotates the backing instances as needed. That is the situation that we ran into where the webhooks would work until AWS changed the backing infrastructure and therefore the IPs returned from DNS lookups. We are running SonarQube in a docker container and the container for 8.9 (the new LTS version) has a change to make it so java only caches DNS lookups for 5 seconds instead of infinity. It may not be your issue but it certainly sounds very similar to what we were seeing.