Foliage does not move with mesh ( in editor )

When I move a group of objects in the editor, which have foliage painted on them, the foliage does not follow correctly.

( I moved the rock to the right, the foliage is copied, but the old version is left behind ).

Anyone have a solution for this? - Thanks.

Bump. So in fact, it turns out, the lump of foliage left behind contains 3 copies of the original. But if I look at the number of actors placed with the foliage tool, before and after, it says the same… :-/

I can move other rocks I covered at the same time, no problem…