Quickly looking through the Ring code, it appears that when it reconnects it re-parses all the device states. You have it set to cancel Alerts when ring disarms. Well, ring is parsing that the state of the system is disarmed, so it sends a cancel alert message.
This will only be a problem if ring disconnects while there is an alert happening. I assume that ring app has to reestablish connection every 4 hours? In that case, there really is no way of doing this other that the way it is being done. There is no way to check the alert status within Hubitat other than having already subscribed to the event and keeping track of it.
@codahq I am curious....if you are tying ring into HSM, why do you have to cancel alerts when ring disarms? Won't ring also disarm HSM therefore canceling the HSM alert as well? I think the action of canceling the alert might be superfluous.