I am using the Map Tour template hosted by ArcGIS Online. I am using the topographic base map. I have a problem with the zoom levels. While I am viewing locations in the United States, I can set the zoom level as high as I want. When I start viewing locations in Europe and Japan, the base map is blank at levels higher than Level 13 (1:72K). I can see the place icon but no map.
As far as I know the Topographic Basemap has quite consistent data at high scale in the US, Europe and Japan. Maybe you are using the Terrain basemap? How is your webmap displaying in ArcGIS.com viewer? If the basemap hasn't the same behavior in ArcGIS.com and MapTour let me know. Otherwise i hope you will find another basemap that fits your need.
That's the interesting thing, in ArcGIS Online, the map functions perfectly. It is only with the story map application that I have problem. I have also made several versions of this to tweak other functions, and they all have this same problem.