Those MB jacks are definitely shady. i had my car roll off the jack twice in one day. The jack breaking may seem trivial but if you were changing your tire you might have had your feet or hands under the brake assy for some reason. i think that the death of your jack is a good opportunity to get a better jack. maybe a small hydraulic or a scissor jack. i also keep one small , medium duty jack stand in my trunk just in case some thing like your jack incident occurs.
you are fortunate it wasn't worse.
Karl.
other pitiful features of the MB: Window regulators, AC.