It would only be Something to worry about if you are seeing this continuously happening. If it was showing only during the upgrade, hasn't since, and you aren't seeing anything showing up within support tools on the database section either, then I would say to ignore that.
Duplicate key issues are related to the database itself. If you look at the support section, I suspect you likely have warnings there on that section you should address with your host. Unfortunately your access on file is not up to date, so I was unable to confirm that