off-by-1 error when reordering buses by dragging

If I drag a bus down the bus pane to reorder it, it will often be moved to one row lower than where the orange indicator line is. 
 
To reproduce, open a project with multiple buses (>6?). Drag a bus, say bus B down so the orange maker puts between bus E and F. Bus B is now Bus F. It should have been E.
 
    Start   Expected   Actual
A: 1        1              1   
B: 2        3              3 
C: 3        4              4 
D: 4        5              5 
E: 5        2              6  
---------<=orange line
F: 6        6              2
 
This doesn't happen if you drag a bus down only one row. Actually it does. The orange line indicates you are dragging it zero rows down (by indicating it will be above the row below) but in fact the two rows will swap. This is less confusing because the animation leads me to think this is the correct behaviour. But the results don't make sense for large moves. 
 
Correct behaviour: the bus should be inserted at the orange line.