The moving bar, that displayed when clicking on the move button not the DnD one, in some cases is drawn far away from the cursor, as if the offset would take into account the scrollbar distance from the top (see attached screenshot). It also seems that this distance is summed up every time you scroll down the page so that when you're working on lower regions of the page and start dragging some component there the moving bar becomes completely hidden.
The issue happens only on webkit browsers (latest FF works fine and I did not test IE).