Possible Causes
One of the Record Fields is referencing a field on the wrong entity type. When selecting a field on a Record Field, sometimes there are duplicates. These duplicates are actually different fields on different entity types.
Example: If a Record Field belongs to the contact entity type but the field selected is a customer field.
Solution
Narrow down which Record Field is causing the issue by deselecting Record Fields one at a time until the record is able to be created. Try selecting one of the other duplicate fields.
Debugging Steps
Narrow down which Record Field is causing the issue by deselecting Record Fields one at a time until the record is able to be created.