Content of D&D-Panel in Firefox & IE interacts weird

[HPEdag]

I use DDPanels and have scrollbars inside my panels.When trying to scroll D&D reacts in two different weird ways, depending on the browser.
In Firefox when I click on the scrollbar to scroll the panel is dragged at the same time. If I drag the Panel far enough so it can be dropped in a target area, it will be dropped. So both the scrollbar and the D&D module react to the mouse events. This also occurs when trying to mark text in a textArea in the Panel. The text is marked but at the same time the Panel is dragged.
In IE11 when I click on the scrollbar and drag/scroll it normally, but when I then let go of the mouse button, the panel is attached to the cursor like a dragging object. If I click again it reacts the same way it would if I were D&Ding normally and let go of the mouse button.

I hope I could make the Issue clear.

Edit: This is in Vaadin 7.6.4 with this addon's latest version