The flashing SES light means that there is multiple misfires. And that would be because of the smashed spark plug. But the spark plug probably got smashed because you shipped a piston. This means that you were probably running with too much knock, which caused the top lip of the #6 piston to chip off. This chip was then slammed against the spark plug and closed the gap. But your bigger problem is now you have a piston with a chip that is going to only get worse.