Notification volume changes by itself

[asdfasdfgasdfadfs]

The notification sound keep going to vibrate (as seen in the screen shot below). Even if I manually slide it to the right, so that I can hear the tones of an incoming notification. the next morning I notice that it goes back to the same position it is in the screen shot. Anyone else have this issue?

 

[pkcable]

I do not have this issue. Of course I turn my notifications off!