In the same logmon profile, I've included two watcher rules: one for a non-clear alarm severity (e.g. major, critical) and one for clear, and enabled 'Send clear alarm' for the clear rule, but the clear alarm sent by the probe doesn't clear the previous alarm.
The solution is to set the two watchers' suppression ID's to the same string. Your two different watchers can send completely different alarm messages. As long as they have identical suppression ID's, the NAS will put them together and the clear will be associated with the prior critical alarm.