While working on a project where I needed to test multiple geo.json files, each time a geo.json file was deleted from Media/FeatureCollection, and a new geo.json file was added. All the polygons of the old geo.json remained in the FeatureCollection. After not realizing this about 5-10times, app kept crashing upon trying to add or delete geo.json files or trying to delete the entire FeatureCollection. With about 200 countries total & 5+ copies of each (example: India, India1, India2, India3, India4…), there were maybe about 1,000 polygons remaining in error which could not be deleted as the app would crash upon attempting to do so. The only way would be to delete one polygon at a time. Reverted back to an earlier version. To get around this error for future, always delete FeatureCollections (not just geo.jsons) and create a new FeatureCollection before adding a new geo.json file.
Great. You discovered a developer needs to clear the existing 'FeaturesCollection' before replacing it with a new one using a geojson file.. This is not a bug; this is the way the Map tool works. Others will appreciate this tip codo.
Regards,
Steve
Oh, thank you very much! Still learning. 
Had a hard time finding resources to learn about all the ai2 tools/features from watching others. Sometimes the MIT ai2 resources don’t make sense, need even more basic laymen’s terms. 
