Steps to replicate.
1. Get this mod https://mods.factorio.com/mod/Updated_Construction_Drones (Although any similar mod will probably work I only tested this one)
2.Place down factory building.
3. Mark it for deconstruction.
3.Let the funny robots deconstruct the building they'll throw a duped factory building in your inventory.
4.???????
5.Ya duped the building.
