Word 2010 Equations Alter Themselves without the Approval


I regularly use Microsoft Word 2010 to write long, technical documents. One of many annoyances is that equations alter themselves without my approval. For instance, characters sometimes completely disappear. The most common issue, however, is that my vectors, which I always write in boldface but not in italics, occationally (and seemingly randomly) turns up in italics when I open a document I have previously saved. (Before I saved it, all vectors were in boldface but not in italics.)

Before I save the document:
Before I save the document

When I open the document later:
When I open the document later

Is there a known solution to this problem?