I've been experiencing the same lately. It happens when swiping the mouse and lifting it after. In my case I found out it's caused by SAB "OFF". When I turn it to 0 or higher it doesn't happen
I've also tried a different controller connected to my XIM Apex and that also fixes it. So I'm guessing it's a controller drift problem.
But it does make me wonder why SAB affects right stick movement at all, when it should only affect movement.
