Alert Action: Execute NCM Action

I am having a curious problem with an NPM action in one of my alerts. I have an alert configured that performs a couple of actions:

1. If 'Monitoring' custom property is set for an interface,
   1. Execute NCM action that SSHs into a device to perform a 'show interface' on the affected interface,
   2. Perform an HTTP POST action to our ticket system with the ${Notes} of the output,
   3. Every four hours until 'Monitoring' custom property is unset

The alert itself is being triggered, as we get updates in our ticket system. I can also go into the 'Transfer status' tab in NCM and see that the alert is being run and the output is being gathered. The problem is with the output that it posts into our ticket system. It appears that the ${Notes} (actually, ${N=Alerting;M=Notes}) is not updating with each successive run of the alert. I've checked the actual alert details in NPM and I can see in the "History of this alert on this object" resource that new output is being populated every four hours, but the same data continues to be posted in our ticket. Any idea what is going on here?