I created a demo: http://pastebin.me/584b9a86d715c9ba85b7bebf0375e237
When the scroll bar is at the bottom and you drag items to sort them, it causes the scroll bar
Lol, looks like this still isn't patched 4 years later. Here's the ticket.
Adding onto @Carl M. Gregory's answer, to fully take advantage of a dynamic container instead of setting it on a fixed height, i would edit the jquery.ui.sortable.js core file.
Simply move back line 228. this._createPlaceHolder...
before line 208. this.helper.css("position", "absolute");
Thanks to Honda on the jquery ticket portal. Am using Sortable.js version 1.10.3.