I read a comment about button rattle in the reviews. One or two small patches of electrical tape on the back of the button fixes it. I have two layers on mine. Put the tape on and rub it in with the butt end of tweezers or similar to get it into its final thickness over the dimple on the back of the button.

A very thin o-ring around the forward facing side of the button might work too. I don't have any o-rings small and thin enough.