I'm not aware of a difference for how Word 2013 and Word 2010 treat form fields and have not had a similar problem as yet. Is your Word 2013 security protecting the entire content as locked for editing, showing in reading view or macros disabled?

Perhaps you should upload a copy of your form so we can test it on Word 2013 to see if this is a problem for others or whether it is something on your machine.

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Andrew Lockton
Chrysalis Design, Melbourne Australia