No, the problems happened over time. The doors could fall of a new one. Like your car no matter how much you do you cannot prevent things from happening, unexpectedly. Maintenance does not mean that you replace things before they break. It means that you do what is necessary to extend the life of whatever object you are charged with maintaining. Not everything can be anticipated.
The example is the door situation. How many doors total are there attached to the fleet of trains at WDW? Collectively, how many times over that time do you estimate, over that same 30 years, have those doors opened and closed? How many times in 30 years have any fallen off. There are millions of pieces that make up a train, how do you anticipate that something that never broke before will break now? I think you know that answer just by the objects in your own home. I'm not sure why people want to insist that Disney property is immune from the same forces that all the rest of the world has to live with every single day. Also why do we feel the need to point a finger and assume something that we know nothing about without the specific experience and complete knowledge of those particular mechanical objects?