Hi, I have the same issue. Custom fields are not displayed in the REST API, only when “Show All Fields” is checked. Switching individual fields on or off has no effect.
Rollback to 2.7.31 from 2.8.X is required.
I wanted to capture an email address before revealing the rest of the form (a price calculator). I have moved away from that for now, but is it possible for a “next” button to capture the data entered up to that point, before the submit?