Previous to 21.11, when you would duplicate an item record, the date last seen would be automatically updated. This no longer happens - the date last seen is retained from the original item.

To replicate:
From a bib record with an item attached, select Edit - Edit items
From the actions tab, select duplicate
Update the date accessioned and click save
From the Normal tab, note that the new item has an updated date accessioned, but the date last seen has not been updated.

This behavior is now different from when adding a new item - when a new item is added, the date last seen is automatically set to the current date.  This is the expected behavior when adding an item.