It is difficult to avoid the duplicate site problem, but fairly easy
to resolve it.
Make a backup of your data before you start.
From the main screen choose Sites (Maintain Information About Sites)
On the Maintain Sites screen choose Utilities (menu item)
Select the 'duplicate sites in the left-hand list and the target site
in the right-hand list.
Click [Merge Sites] and make sure what the program says is logical
before click [Yes]