PSA: Changes in alert severity don't work logically with ticket closing. Be careful...

I can't speak about Zendesk integration specifically but other ticketing systems would open a fresh ticket on an active alert and not attempt to update an existing ticket. If you are using Custom HTTP Delivery, is it setup to generate a new ticket each time?

Imho, I don't suggest allowing LM to reopen old tickets but generate new ones. Otherwise you will have LM reopenning year-old tickets. Not related to this, but I also don't suggest auto-closing tickets. That can lead to not seeing issues that are intermittent or flapping. That is especially the case for alerts that auto-close themselves like EventSources. Unless you normally review closed tickets, I guess.