Charles, thank you for your reply. The bullet styles, like headings in templates I create, were created by following Shauna's pages, with levels, in a list style. We already use levels 7 & 8 of the built-in headings, leaving only 5 and 9 to accommodate a (usually) three-level (occasionally four; not my choice) bullet structure.

Perhpas I didn't make clear, that this one document, hosted on SharePoint, is the only time I have seen this happen, though I don't use the nav pane, myself. If I create a new Word doc, the behavior is not replicated. The document in question is a 200-page proposal doc, with several writers. I suspected that the problem is some sort of corruption, unless you're telling me that this behavior is normal (which doesn't cohere with my experience with list styles, Outline view, etc.), and may perhaps be fixed with the usual copying minus final paragraph.