Why does my Galaxy Note 5's sound keep turning back on when I set it to vibrate?

[AC Question]

I have my phone on vibrate pretty much all the time but I recently got a Galaxy Note 5 and I've been noticing out of no where the sound will turn back on. I'll be sitting at work and all of a sudden the ringtone or notification tone will go off. Then I have to go back in and set it to vibrate again.

 

[B. Diddy]

Welcome to Android Central! Try booting into Safe Mode, which temporarily disables all 3rd party apps. https://support.t-mobile.com/docs/DOC-23216

If the problem disappears in Safe Mode, then something you installed is causing the problem. You may have to uninstall apps one by one until the problem disappears. If the problem persists in Safe Mode, then it's more likely to be a hardware or firmware problem.