new → open
sortable: Strange behaviour on big item and overflow:scroll → Sortable: Intermittently unable to sort while dragging and scrolling
I don't believe this is caused by #5039 as it has to deal with the page scroll and this is caused by scrolling within a single element.
This also has nothing to do with the size of the items as I can recreate the problem with much smaller ones, here's a reduced test case http://jsfiddle.net/tj_vantoll/Sb4GT/.
The issue is that when you scroll, occasionally when scrolling you have to shake the mouse a bit for it to recognize the new positions of the sortable items. This is most noticeable when scrolling up but occurs in both directions.