Hi @artfulcat
I believe it’s because the database doesn’t have the reference key for the new custom field entries. This page should give you more idea about it (under the Basic (field key) section): https://www.advancedcustomfields.com/resources/update_field/#usage. To fix it, you need to use the field key instead of the field name like your solution.
If you want to show certain the field groups or custom fields, I think you can use the “field_groups” and “fields” options. This page should give you more idea about it: https://www.advancedcustomfields.com/resources/acf_form/.
I hope this helps 🙂
