Welding pictures

I want to do the following (to get finaly a picture useable as wallpaper for a system with 2 monitors, so please check only the lower part of the pictures)

I want to insert (via VBA) a picture, intersecet it with a shape to have only a picture with an upright standing woman:

This works fine so far. As next step I duplicate this picture and place it left to the master:

This works also fine.

Now I want to weld both pictures as one object (to assign the left part a transparency). But what happens then:

I do not see the girl twice anymore, but that part of the picture I cut of before?

Is this an handling error or Corel Bug?