It didn't "malfunction" so much as was overloaded WAY beyond it's designed capacity and was broken by an unruly MOB!
An escalator shouldn't break like that even if loaded down with as many first week weight watcher biggest loser contenders as will fit.
And they didn't really look unruly, not that that should make a difference. Mere human muscle power shouldnt be enough either, even if they are sumo doing synchronized jumps.