(1) Any defect in the structure, materials, works, plant or machinery of which the employer or the agent of the employer could have had knowledge by the exercise of ordinary care.
(2) The neglect of any person engaged as superintendent, manager, foreman or other person in charge or control of the works, plant, machinery or appliances.
(3) The incompetence or negligence of any person in charge of, or directing the particular work in which the employee was engaged at the time of the injury or death.
(4) The incompetence or negligence of any person to whose orders the employee was bound to conform and did conform and by reason of having conformed thereto the injury or death resulted.
(5) The act of any fellow servant done in obedience to the rules, instructions or orders given by the employer or any other person who has authority to direct the doing of said act.