I use DND mode a lot with my Galaxy S6 edge, every day at work to avoid getting interrupted by phone calls, messages, etc.
It has been working great, up until the most recent Android update (I got v7 a week or two ago).
What happens now is that 10-20 times per day, the phone shows a notification "your phone is in DND mode and you might miss calls". As if I didn't know that? That's the whole reason I put it in DND.
Anyway, this notification keeps coming back constantly and needs to be clicked on to make it go away. It is quite annoying.
I did some google searching but couldn't find an instruction for how to turn off this notification.
It seems to come back every 30 minutes or so, roughly.