AMuise-esristaff Ok - that worked after two attempts:
1) Save As on the map, shared it with the group, and removed the old basemap from the group = fail message but feature shows up
2) Completely new map, added the "public_input_points" feature layer, shared it with the group, and removed the copied basemap above = success!
Next, to test the 'schools' layer, I added that to the new map, refreshed the app, and received a submission failure again! So, as you started to figure out, there must be something wrong with the schools feature collection.
Next, I uploaded the 'schools' data as a shapefile (from a local zip) directly to the new map. When I refreshed the app, the schools only show up in the inset map, and the report form submission fails again.
Finally, I published the 'schools' shapefile as a feature service, added that to the map (and removed the shapefile), refreshed the app, and everything works! The schools show up in both maps, and the report submits correctly! The 'schools' feature service was from a feature layer this time, not a feature collection.
That was a lot of strange debugging, but I really appreciate your help! Hopefully this is a helpful test case and you can determine why the schools only appeared on one map, and why that data would be preventing my app from accepting new data points for the only editable layer.
Thanks again! And let me know if you need any more feedback.