My wife's Note 5 is still on Lollipop and she's recently having this problem where no matter whether she is on silent or vibrate, her notifications(from various apps) are still sounding out loud. Any fixes would be appreciated.
Check the settings, especially the Do Not Disturb. Maybe that was pressed from the status bar. It was hidden in mine until I moved it because I like it.
Also go to those apps and see if there's a setting and what it is on. Maybe an update to the app changed the settings she had. It happens.