Issue with dragArrange pugin

Issue with dragArrange pugin

Hi there

I have a small problem with the drag function.
I have set the elements-container div
then the .draggable-element 
Then when I drag one element, which is in the middle of the page, the element appears at the top of the page.
It doesn't stay below the "move like" cursor but it flies like a kite above my mouse.
What's wrong with the css ?

Thanks for any help
Fred