Annoying repeat notifications for incoming SMS

A few weeks ago I started getting duplicate notifications for incoming SMS. I only get the SMS once, but every 1-2 minutes the notification tone sounds for a total of about 5 times, and then it stops.

Happens with both stock messaging and HandCent as default. HandCent has an option for reminders, but it's off.

No android updates or changes in launcher or messaging app when this started to happen. I have installed some apps along the way, but no idea what I installed around that time. I had Notification Manager installed (don't remember if installed before or after the problem began), but now I've uninstalled it and the phenomenon continues.

Any ideas about what might be causing this and how to make it stop?

Galaxy S5 SM-G900F - rooted
Android 4.4.2
Nova Launcher