You will see this happen with tracks in the Edit window that are near the bottom of the window. It happens because Pro Tools needs to make the entire travel path of the fader visible when it appears, but has no way to "jump" the mouse pointer in relation to that path in order for the pointer to match the current position of the fader control. The software designers had to choose between two evils in this case, either make the fader path partially inaccessible by having it hang off the bottom of the screen, or have it work the way it does now.The software is intentionally coded to compensate for the way it works now by not applying the immediately visible change in volume until you actually move the fader, thus if you notice that the track you are adjusting is too close to the bottom of the window and the "misplacement phenomena" is occurring, you can abort the effort by simply not moving the fader and releasing the mouse button. You can then scroll the window so the track is in a more optimal position for making fader adjustments.