The answer to your question is already in this list. Search February's archives for "dbcheck", "4.7.5", and "bug 13228". Also read the Release Notes for version 4.7.5. You should run "samba-tool dbcheck --cross-ncs --fix --yes" and those dangling entries will be removed. Then run dbcheck again to see if all is nice and clean. As always, it is prudent to do a database backup before proceeding.