if a feature is selected twice the selection symbol dissapears and the feature is not visible anymore until another feature is selected.
Do you mean, double-click or clicked once and after some seconds twice?
I had this beaviour, too. The reason was, that the click-event on the map (to select a feature) called again at the second click. You have to denie the click-event, when a graphic is selected. I overwrote some functions of the Editor-Widget and add some functions that check if a graphic is selected and the second click is set on this selected graphic. It was a bit tricky, but finally it works.