2010 TOYOTA MATRIX Seats Problems

WHILE MAKING A SHARP MANUEVER FELT A 'POP' UNDER THE DRIVER'S SEAT. SEAT THEN HAD A SLIGHT ROCKING MOVEMENT, AS IF LOSE FROM THE FLOOR (E.G. A SMALL AMOUNT OF 'PLAY' WHERE THERE SHOULD BE NOTHING BUT A SOLID CONNECTION).. WHEN DUE FOR INSPECTION THE VEHICLE WAS FAILED DUE TO VA REQUIREMENTS. OWNER (SELF) DETERMINED THE 'PLAY' WAS BETWEEN THE SEAT PROPER AND THE SLIDING BRACKET TO WHICH IT IS ATTACHED. HE THEN THE PARTIALLY REMOVED PLASTIC COVER FROM THE DRIVERS SIDE OF THE SEAT AND TIGHTENED A LARGE-HEADED SCREW (ABOUT 1/2 INCH) WITH A TORX HEAD USING THE APPROPRIATE BIT MOUNTED IN A SCREW-DRIVER HANDLE. THE SCREW GOT TO NEARLY THE POINT OF BEING 'TIGHT' WHEN IT ABRUPTLY BECAME LOOSE AGAIN AS IF IT WAS 'STRIPPED'. IT WAS THEN TIGHTENED LESS FIRMLY AND THE VEHICLE WAS RE-INSPECTED AND PASSED. ABOUT 2 WEEKS LATER THE 'POP' SENSATION REOCCURRED AND THE...