This problem is seen at locations that use export and import to maintain two different Noah databases; maybe between offices or between an office and a travelling laptop. To experience the problem, the location would need to have one computer using Noah 4.7 (or earlier) and the other machine using Noah 4.8, 4.9, or 4.10.
This issue happens when you import and merge data from Noah 4.7 into Noah 4.8, 4.9, or 4.10. In those later versions of Noah, the action is seen as new and not merged. This creates a duplicate of the action.
In addition to duplicate actions being displayed, the database will grow faster, especially if the importing and merging is done over and over.
To prevent more duplicate actions being created, update the Noah 4.7 machine to Noah 4.8 or higher. End of support for Noah 4.7 is November 30, 2019.
This issue has been fixed in Noah 4.12, this means that Noah 4.7 exports can be imported into Noah 4.12 with no duplicates being created. Updating to Noah 4.12 does not remove the duplicate actions.