Styles get corrupted when a document that was created in a newer version of Microsoft Word is edited in a older version. Basically the newer version brings in the style definitions (embedded in the file) that the old version doesn’t “understand” and cannot interpret.
To fix this problem go to Styles and Formatting pane and select Show: Custom; find all instances of the char style and delete them (one at a time)
Sometimes the files cannot be deleted and you can run a macro to remove them:
Dim style As Word.style, doc As Word.Document
Set doc = ActiveDocument
Set style = doc.Styles.Add(Name:=”replaced”)
On Error Resume Next
doc.Styles(“Name_of_the_Style”).LinkStyle = style