When the story map crowdsource app builds the web map and adds the feature layer into the map, the feature layer is given a unique ID in the web map JSON. This ID is then saved in the application configuration so the story map knows which layer to work with. If you add a new feature layer to the the current web map that the crowdsource builder created, you will need to manually switch out this layer id.
Also, the crowdsource app is set up to recognize specific field names in the data. If you changed the field names, the app will no longer recognize that data unless you also update that in the application configuration. Because this is still a Beta, we don't have an interactive builder for this. You will need to open up the application configuration through AGO Assistant and manually edit JSON to read the new field names.
By changing the field name in the feature service, you will not change the form input labels in the crowdsource form, this will only change the name in your database. If this is what you're trying to accomplish, I can send you instruction on how to do this. If you are just trying to change the form inputs and placeholder for your users, you can follow these instruction: https://developerscorner.storymaps.arcgis.com/how-to-personalize-your-crowdsource-story-even-more-a9... .
