it looks like you are doing the same thing. I have attached a link to a video for you to look at demonstrating the issue. Hopefully it will come out clear enough for you to see, although the frame rate is a bit slow.
Firstly I undock a pane and drag it. You will notice that the further the mouse pointer gets to the bottom-right of the screen the further the pane gets from the cursor. The closer it gets to the top-left of the screen teh closer it gets to the cursor. I then release the pane and then drag it again whereupon the expected behaviour is displayed.
I hope this helps you to get to the bottom of the issue.