The differences in the information provided by the Seoul Subway app and the actual locations of the elevators has got to be renovations in the subway stations that have not been reflected in the apps. Every subway station in Seoul is designed with accessibility in mind. While most stations are equipped with elevators, the few that aren't have installed mechanical lifts to help navigate the stairways. I have traveled to Seoul and can confirm some of them, but I haven’t been to all subway stations.