Dragging a story from Icebox to bottom of Backlog moves it to Current

Here's the setup: based on the velocity, there is room in Current for one more point; the Backlog has Item 1, Item 2, and Item 3 (in that order), each with 2 points; and the Icebox has Item 4, rated at 1 point. Now, dragging Item 4 between (say) 2 and 3 does the right thing: it inserts Item 4 into the Backlog between the other two items. Dragging Item 4 from the Icebox to above Item 1 (indicating top priority) also does the right thing: Item 4 gets moved automagically to Current. The problem occurs when dragging Item 4 from the Icebox below Item 3: instead of the expected behavior (insert Item 4 after Item 3 in the Backlog), Tracker moves Item 4 immediately to Current.

Placing Item 4 in Current is incorrect, since Item 4's position indicates lowest priority, not highest. Immediately moving Item 4 back to the lowest position, from Current to Backlog, works fine, as do movements within the Backlog; it is only the transition from the Icebox to Backlog that has the problem.