I've seen this on nagios and on my current icinga installation.
I have flap detection turned on. I have my contact definition set to:
service_notification_options w,u,c,r,f host_notification_options d,u,r,f,s
When a service starts flapping, the web interface says notifications are being suppressed due to flapping. I don't get a notification that says the service is flapping.
But I want that notification - because otherwise I'm not getting any notification at all that something is up with the relevant host/service.
Am I misconfiguring things?