notifications - Phone won't shut up even in Vibrate/Silent mode

If I set my phone to Vibrate or Silent modes, it's still making audible notifications for GMail, Hangouts, Waze, and maybe other things.

It has worked as expected for years, and then started doing this in the last few weeks. I don't see any other setting anywhere that adjusts this.

All 3 of the main volume controls are at zero. Is there somewhere else I should look?

The loudness of the notifications matches the loudness of the notification slider when it's not muted. Like if I set it to high level and then go to silent mode, the notifications are still high level. If I set it to the lowest level and then go to silent mode, the notifications are at the lowest level.

CM11, Android 4.4.4, Samsung Galaxy S Relay