Notification sounds every 10 second until I answer it, how can I stop this?

[AC Question]

Notification sounds every 10 second until I answer it

My HTC M8 is now sounding the notification sound every 10 until I answer it, even overnight, instead of just once.I recently synced the new Fitbit Blaze and disabling notifications in the app didn't help. I have not been able to figure out how to get the notification sound to only sound once. Very annoying and draining the battery. Any help appreciated.