If you happened to be working with.... KML data (or any data with large description strings) and transitioning it into the ESRI Story Map toolset, there is a very good chance you hit the the dBase 254 character length limit with the ESRI Shapefile upload. Shapefiles are always a terrible idea.
the solution: with GDAL or QGIS (alright, even in ArcMap), one can use GeoJSON as an output format AND import into the story map system- with complete long description strings!
Merge vector layers -> save to file -> GeoJSON
arcpy.env.workspace = "/desktop/arcmapstuff"
arcpy.FeaturesToJSON_conversion(os.path.join("outgdb.gdb", "myfeatures"), "output.json")
ogr2ogr -f GeoJSON output.json input.kml