Same problem here.
After extensive digging, I've discovered the source: It's one of your apps that you had NO CLUE had access to Notifications. There's no way to tell which one it could be, but if it's not the obvious (in my case it was the Bubble Blast game, which I couldn't even figure out what it was trying to notify me of, and it never did this until now), you have to go through each one, starting with the ones you've updated most recently, go into the settings for each app, poke around, and if nothing else, uninstall non-critical apps until the light blinks for normal notifications only. Hope that helps!
