Mine started doing that today. I originally had the sound/vibration alerts off because I get so many of them. Now I'm getting 2 notifications for everything and one is a vibration. Very annoying and nowhere to turn it off.
DNSet worked so far!!!! My WiFi is ATT Uverse with faster speeds than expected bc no one else in the neighborhood uses it. Chromebook and laptop are fine. The galaxy was slower than dialup on WiFi.