FWIW I have had this issue occur numerous times with AMT. However, there have been differences. Sometimes the dupes are true copies and other times they only appear in the tree graphic. If the latter, delete one and they are both gone! I've noticed different causes and have learned to delete carefully. I first change one of the names by putting an X in front of the one I want to delete. Sometimes (magically) the X will appear in front of both and the dupe is obviously an apparition. Then I hunt for the cause and often find an extra mother, father or spouse. If working with multiple tabs, be sure to refresh (F5) to update before deleting. HTH...
Sturdy2
Sturdy2