Over the decades, you got various companies involved in making escalators and you've got Metro varying between internal repair crews and contractors. They're dealing with old equipment, which of course is prone to break down, and the repair crews don't even know what's busted or who made the busted parts till they tear the things open. Then sometimes they have to go back to the shop and manufacture parts, because the original maker has gone out of business.
I think that maps showing platform details would be useful to visitors, especially to chaperones of school groups, etc. Also useful would be either a compass rose or an arrow pointing North at every metro exit. Emerging from underground is disorienting, especially at night.