That shouldn't be happening, can you confirm? It should flush out the old ones based on the current DNS information. The whole point is to automatically update the alerts based on the latest DNS information so you don't need to manage that yourself.
Sorry, that obviously shouldn't happen (both domain not updating and support falling through). We use Shodan Monitor for our own infrastructure and haven't seen that issue (or heard about it from our other customers) but I'll keep an eye out.
