Auto placement into empty layer window

[fbacc01]

Hello there,
i dont know if i can explain it correctly but sometime arena make screen or duplicate one layer window and automaticly put it into empty window in a layer (sadly i dont have a screen for now).
What happen is overlay if something is in a layer above and layer below is empty. If everything is full in bottom layer than put it on next empty collumn what is not issue for me. It is bug, or some bad setting?

Thanks guys.

[Zoltán]

Some screenshots would help a lot to see what's happening