Don't Use the "No Markup" Option in Track Changes
In Word 2013 the Track changes feature contains the option to display No Markup. Do not use this feature if you are also using the Citavi Word Add-In.
The option No markup makes your changes look as if you had already accepted them. However, text that you change is still present but is simply hidden from view. When this option is selected it's possible that a reference that you inserted with the Word Add-In and then deleted is still present in your Word document. This keeps Citavi from being able to apply certain citation style operations related to ambiguous references or reference numbering. In addition, the deleted reference will continue to appear on the Citations tab.