Yeah I've been getting this mostly with hangout messages. I'll got to send a new message to someone in hangouts and I'll have a new incoming that I never got a notification for. Not even in my drop down.
Yes. I'm having reception issues so I though maybe it was related to that. I've been expecting calls, sitting there with the phone in my hand, with what appears to be decent reception, and I'll all of a sudden get a voicemail notification.