Battleship view renaming

I am trying to troubleshoot a script I re-created from an Autodesk presentation many moons ago, 2015 vintage, that essentially automatically renames/numbers views on a sheet according to the alpha-numeric grid that is located on the outside perimeter of our title blocks.
The script is working great with exception of, when two views occupy the same block in the grid the script is supposed to rename one of them to example: “A4dup” so Revit doesn’t throw the error message saying two views named the same.
Something is not right I believe in the REMOVE DUPLICATES SECTION, and I think, specifically the archilab node Lists.DuplicateItemIndices. I should not be seeing empty listing there as my Create Cell Address is not showing empty correct?

Your list levels are off. Your list of locations is three individual lists instead of one list of three items. So you’re getting unique values from each sublist instead of the full list.

You’re getting empty lists there because you have no duplicates. If you’re expecting to see the second M15 value trigger a duplicate, then you’d need to use a list.flatten first as currently these items are in different lists.