Problems with CF_CiviCRM Registration with Caldera Forms
This was my own confusion and I had help from the CF-CiviCRM author. Great support there. 

The problem was related to conditional statements in the form. I had created conditions for the appearance of all the contacts in a multi-contact form, but I hadn't applied conditions to processors. 

I had assumed that the conditions related to the show/hide fields were inherited by processors. That's not the case. Instead, each contact processor had to have its own conditions applied to the group of fields. 

For example. Only process the second contact group if First Name 2 is %first_name_2%. In other words, if the first name of the 2nd contact is blank, don't process that contact group. This is regardless of whether the conditions allow visibility for that contact. The visibility rules were not applied to the processing of the group. 

Lesson learned, and maybe someone else will benefit from my experience.