What should I do about a defective product that threatens to cause a fire, given that pursuing the matter might lead to the dismissal of an employee who is in dire need of his job?

If it is possible to combine protecting people from the harm of the product and not harming the employee, such as withdrawing the product from the market, while advising the responsible person and the employee to repent, then that is preferable. However, if it is not possible to combine them, and it is inevitable either to harm the employee or to allow the product to circulate causing harm, then pursuing the matter is obligatory, because harming one person is lighter than harming the entire society, and this is at the core of trustworthiness.