The circle is shown when you adjust the sliders on the Weights or Mesh Edit views. If you always see it in the center of the screen then it sounds like a bug. Any idea how you got it to stay visible?
Restarting Spine will make it go away. It would be better to move the sliders for the Weights or Mesh Edit views though. See which one makes the circle go away, then we'll know which one has the problem.
