2003 TOYOTA COROLLA MATRIX Visibilitywiper Problems

THREE INCIDENTS - 2ND OCCURRED IN MAY 2014, 3RD IN AUGUST 2014. VERY LARGE, CLEAN CRACKS KEEP APPEARING IN THE SAME SPOTS ON THE FRONT WINDSHIELD WITH NO POINT OF CONTACT. THEY BEGIN FROM THE MIDDLE BOTTOM OF THE WINDSHIELD WHERE THE HEAT VENTS START AND IN A U-SHAPE COME OUT OR AT THE TOP MIDDLE - BEHIND REAR VIEW MIRROR - WHERE HEAT VENTS START - LIKE A SMILEY FACE TO NEARLY THE TOP OF THE WINDSHIELD OR A LINE DOWN DIRECT FROM MIDDLE OF WINDOW. THE FIRST TIME IT HAPPENED I WAS USING THE HEATER . THE SECOND TIME AND 3RD TIME IT WAS PARKED OVERNIGHT BUT NOTHING WAS STOLEN, NO OTHER DAMAGE AND NOTHING TO INDICATE A POINT OF CONTACT SUCH AS A ROCK OR SHARP TOOL. FULL CRACKS APPEAR ALL AT ONCE - CLOSE TO ENTIRE HEIGHT OF WINDOW AND ARE NOT GRADUAL. REPLACED THE WINDSHIELD...