sarahric:
Your screen shot shows you have 2 versions of the ArchiCAD 8.1 Lib loaded. Also, you can change the Information pop up from "List of placed Duplicates" to "List of all duplicates" to see a list of the duplicated parts.
Based on your screen shot, the ArchiCAD 8.1 Lib is the source of most of the duplicates (there are 2 in your Embedded Library), so I would 1st try eliminating the ArchiCAD 8.1 Lib and see if you come up with any missing parts. If so, then one approach is to save an
Archive version of the file (which will save all the used library parts, not the entire libraries), open this file and select the option to "Extract elements to a new folder:" (see in the Help files: Configuration > Archive Files) which will create a folder with all of the used parts. You can then remove the duplicates from this folder. If you then add the ArchiCAD 15 Library back, you can again remove its duplicates from this legacy folder, so this folder keeps the legacy parts while the ArchiCAD 15 Library allows you to have the most recent and up to date parts for adding to the project. The legacy folder could be added to your Embedded Library once the duplicates are cleaned up.
David