I discovered something about cross-references today that took me by surprise. I have a document using outline numbering with a custom style "attached" to each level. In the text, I use the cross-reference feature to reference paragraph numbers (e.g., See Section 1.1). Normally, when I update the fields, the only time I see the cross-reference field code change to the ominous "Error! Reference source not found" is when I delete the section that the cross-reference is referring to. (Operator error.)
Today, though, I changed a one-word heading to a different word and left the style/paragraph numbering intact. When I updated the field codes, all cross-references to the paragraph number attached to the one-word heading changed to "Error! Reference source not found." I was able to recreate the scenario if the heading is one word and I replace the entire word, but not if I only change some of the words.
Is there something I need to do when modifying headings so that I don't break cross-references?