Hmm, depending the duplicate mode your use, if you want make an duplicate go in the triggers and adjust them to make something like this:
Events:
Unit enters region
Conditions
Owner of Entring unit equal to Player 12
Actions
Create a unit for player 12 of unit type of Entring unit at (where you want to put the new unit: for example: position of entring unit) facing Facing of entring unit.
Please note if you want make some changes to the new unit use the last created unit.
If the bug stand pease give me the map (if you are not playing in versions over the patch 1.27) and i will try to fix it
Have a nice day...