One of the specific claims was that a robot intended for packaging lithium cells into battery modules misbehaved and punctured the battery module casings, damaging some of the cells. He alleges that Tesla then simply fixed the robot, and sent dangerously damaged battery modules to be integrated not vehicles. He published a list of Model 3 VINs which he alleges have the dangerous matters modules installed.

There are other claims about unsafe storage of hazardous waste, but that battery module claim is the one that sticks in my memory.