This app uses online tiles from Openstreetmap.org. This violates the tile usage policy that is in place to make sure that the osm servers aren't overloaded with too many requests. Violations like this one lead to the current problem of slow loading of tiles for visitors of openstreetmap.org. Please use another tile server instead that is really meant for use in apps.
I am only a simple member of the OpenStreetMap community. If you have any questions, please contact OpenStreetMap foundation.