moving selected pictures from one album to another

I want to move a selection of pics from one album (actually sub- or nested album) to another - already existing - album. I've used the "cut" and "paste" command from the edit menu and the pictures also show in the destination album but
- the number of pics in the destination album only equals the number of pasted pics and not the total of pics that should be in there (ie. incl. those that have been there before).
- I only see thumbnails of the pasted picures in the destination album
- they are not moved
I tried all buttons at the botom but none of them seems to execute the move. What am I doing wrong??