Analogue-sequencer

I'm currently wondering whether I've stumbled across a bug (I'm on Beta 
39) or a misunderstanding on my part. Can anybody enlighten me?

Here's what I want to do:

I've created a part 2 that I want to duplicate to part 3. I'm in play 
mode. I use part-copy all from play mode -> hold down F2 and select part 
3 as target. Part 2 and 3 are now identical. Everything is fine so far.

Now I'm trying to edit a track in part 3 - I want to create a variation 
of what is in part 2. Now whatever I edit is applied to both part 2 and 
part 3 -> in other words, it seems as if part copy doesn't actually copy 
the tracks, but simply sets a pointer to the data from track 2. Why is that?

What's the proper way to copy a part so I can create a variation of it?

Bye
Martin