Hello,
What version of SEP 12.1 are you carrying??
The Latest Version of SEP 12.1 RU1 (12.1.1000) is taking care of a similar issue:
A notification for "new risk detected" is triggered repeatedly, despite longer damper setting
Fix ID: 2497657, 2212158
Symptom: The damper setting on a notification for new risks is configured for a specific time value. The first risk triggers the notification correctly. Subsequent risks before the damper period time incorrectly trigger the notification.
Solution: The damper option on notifications was modified to prevent this issue.
Reference: http://www.symantec.com/docs/TECH174565
Incase, if you are carrying the SEP 12.1 RTM version, please migrate to the Latest version of SEP 12.1 RU1 (12.1.1000). http://www.symantec.com/docs/TECH174545
Hope that helps!!