The parents of a college student killed in a Tesla crash say she was trapped in the car as it burst into flames because of a design flaw that made it nearly impossible for her to open the door, according to a lawsuit filed Thursday. The new legal threat to Tesla filed in Alameda County Superior Court comes just weeks after federal regulators opened an investigation into complaints by Tesla drivers of stuck-door problems. A fourth was pulled from the car after a rescuer smashed a window and reached in. The lawsuit follows several others that have claimed various safety problems with Tesla cars. In August, a Florida jury decided that the family of another dead college student, this one killed by a runaway Tesla years ago, should be awarded more than $240 million in damages.