The event mapping process checks the eventClassKey and, for any that match, it checks mappings starting with the lowest sequence number. As soon as a match is found, any associated class and/or mapping transform is executed. Event processing then stops. Once a match is found, that's it.
For Zenoss 3.x, most of this processing is done by zenhub so is there anything indicative in zenhub.log? With Zenoss 4, it is zeneventd that does this processing work so that is the log to check.
Cheers,
Jane