That must be an ‘S’ thing. Tried it on my 3 and it just minimises the stations screen. No refresh buttonFinally found the DAB refresh button. Had lost it after update for Model S software.
When you are in the radio page and have DAB stations selected, put 2 fingers in upper right part of screen and pull down and to the left. Keeping your fingers on the screen you can move the radio channels around and the refresh button is hidden lower left. You can press this with the other hand. After the refresh, all DAB station reappear and the button seems to stay in the correct position.