Field value disappears when flattened

I've been using Quick PDF for years and haven't found a problem I couldn't resolve until now.  I have a form that has several fields on it that I need to populate and then flatten for a customer.  All the fields except one flatten with no problem.  The "bad" field reports that it flattened OK and properly destroys the field, but nothing has been placed on the form. 

Has anyone seen anything like this or knows of a workaround?  I can upload a sample of the form if someone tells me where / how to upload forms.

Thanks,

Hans

Thanks for the reply, Ingo.  I did try the NeedAppearance with no success.  It is also the only instance of that field name on the form.  I did, however, discover how to fix the issue by playing with Acrobat along with the flattening code.  I found that if I moved the field, suddenly the field value would flatten correctly.  Acrobat can be rather screwy sometimes.