Holds, but wobbles and breaks

Now, after half a year I use the thing is broken when folding the car mount. It has done the last 6 months good services, but this fatigue can not be true. As stated in the title, it will stop the windshield and never dropped. However, the car mount resonates with inserted phone (Galaxy S2). And no, not on cobblestones, on normal Bundesstaßen- and highway asphalt.