duplicate problem
 

I have a Problem with duplicating Polygon cubes.
I made the wall for my footballstadium with polygon cubes.
After that I duplicatet the cubes in negativ 1 for the other side.
Then I wanted to add any details for the wall, for that I had extruded any faces. But when I did that, the Faces from the other side did the same translation, but why? I never select them and I did not extrude that faces on the other side.
Delete the History was unsucsesfull.
I tryed that in a new project to fix out what it is, but without any result.
Have you an idea!

you probably have duplicated the boxes as instances. Try resetting your duplicate options. I think you will have to make your stadium again though.