In general - consolidate duplicate code into a single place and ensure original duplication site is calling the consolidated place.
In your examples, within a class this would be the extracted method and within a set of classes the pulled-up method within the base class.
In copy-paste code, this would be to remove the duplicates and ensuring that any users now use the single copy (in whatever level this is).
When dealing with different versions of libraries, consolidate on a single version (if possible).