On QT6, when using DragHandler, dragging a scrollbar upwards, passing the pointer through a DragHandler and then releasing the button outside the scrollbar, does not cancel the scrollbar press. So when the mouse is returned to the window scrollbar is still active and page contents are dragged around and/or window is moved.

To replicate add the following to Toolbar in webengineaction

DragHandler {
            onActiveChanged: if (active) {
                        window.startSystemMove();
                      }
            target: null          
          }

This may also happen with plain QML examples, but I didn't find any with a scrollbar in qtdeclarative.