if no window opened, try clicking here.

Here's how you reproduce the bug:

Just open the test window (either by allowing javascript to open it, or by clicking the link). The popup loaded will refresh itself every second. Start moving your windows around, either the small or the normal sized window. Little movements work best. Drag it a bit, drag it again, drag it again, it will start snapping to odd positions. You only have to drag the windows around a few times before it starts happening.

I can reproduce it most often by moving the big window around a couple times, then trying to move the little window.