In a drawing that I have edited many times, I noted a strange (for me) behaviour.

When I open the design any selection of an entity (2D or 3D) and a drag of it, just moves it to the new location.
After I insert some new entities (notably rectangles) the default behaviour changes: any entity drag does generate a new copy in the final location.
Note that I cannot reproduce it on a brand new design (where I have just a drag/move), seems to follow *that* drawing.

Why does that happen?
How do I revert to the drag/move default?
I'm running version 5.1.5.0

Lou