The light consists of two parts: the light unit including batteries (rather heavy) and a part mounted to the frame of the bike. both units are just clipped into each other. due to the high weight of the light unit, mechanical shocks (like the parked bike just flipping) causes the light unit to detach from the frame, distributing light and batteries all over the place. Happend now several times. Such a high failure probability is not acceptable for a safety relevant component like a tail light.