I where in the expectation iy would be fixed now.
But duplicate a parent entity with a child entity
attached is not going to duplicate the child entity.
You can select the child enity or not select it. It only copy the parent entity !
ADD: Now it get a bit interesting. I start to rotate my object. at that moment i think i did hit by accident soemthing invisible. I moved it. And guess what, it;s the other child entitiies.
The are copied, but stay complete invisible !
A pile of the copies are stack inside the orginal one. SO the where copied but not moved to the new location when i made the copy.
Now cleaned all the copies out manual.