I'm not sure if this is really a bug, more like an annoyance, but whenever the UI is being moved, the mouse cursor moves at a slightly faster speed than the UI. While that isn't a big issue, what happens if the cursor comes off of the UI is.
One thing that happens is the camera will move since you are holding the left mouse button while dragging. How extreme the movement is depends on how fast or slow you happen to be moving the mouse at the time.
Also, what's more annoying is that it will also change to edit a different shape if the cursor happens to roll over a new shape. This also happens when using the scroll bar while editing a texture. That can be really frustrating when you put a lot of work in to editing and then it is all lost. That has taught me to use Adjust a lot more often while editing textures.