I had a problem last week with a couple of forms that have fields that inherit values from fields on the document that is open when the new document is created. On one form, the field values were set properly, but on the other they were not. The form being created is a response-to-response form. The form that worked was a response form, so at first I thought the problem with the form that was not working was because it was a main form. I discovered that wasn't the problem when I was able to get that form to inherit a text field.
The fields I was trying to inherit were names fields. And the two "parent" forms used different names for the names I wanted to inherit. On the form that worked, the fields were named the same on that form and on the child form I was using for my new document. Aha! I changed the field name on the child form to match that of the form that didn't work, and that started working; of course, that also broke the other form that worked previously.
What I ended up doing was adding a Computed For Display field to the child form that was named the same as the field on the form that didn't work. It has a value in it when a new child is created and is blank at all other times. I then reference that field in the formula for my name field and it works for both forms.
I couldn't find anything that said Names fields inherit differently than other fields. but they apparently are different. After spending about 4 hours trying to figure it out, I figured I'd write it out here, just in case it comes up again.