Back in the mid 80's, the Mark IV version of the Silver train had a side tire go flat on the Epcot beam. The rubbing of the tire caused a fire in the last car. Folks had to be evacuated to the roof of the train, and to a safer car. Thankfully, no one was hurt.
One good thing that did come of this incident was that each train was retrofitted with enhanced safety measures... roof hatches, intercom phones, fire extinguishers, and a primitive version of the Allison Heat Detection System. The (then) new Mark VI trains were designed around these safety measures, and even more were added. Beam Contact sensors, a better heat detection system, and a multiplexing monitoring system.