Created attachment 64501 [details] Page the problem occured and the code that is generating the duplicate. There is a duplicate Serials tab when using a Saved Report. There doesn't seem to be a way to delete one of the duplicate tabs. I viewed the source for the page and found that there's a Report Group "SER" and a group "Serials".
Apparently it's an "Authorized Value" and can be removed from the REPORT_GROUP category.