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This happens when an asteroid group is under the button and the tooltip is trying to tell you that you cannot fly through the asteroids. Just have to move the map so the button is over empty space.

That is one of the scenarios where it happens, and that work around does work, but far more often I have the "how to shoot a ship" yellow tool tip dialog on the screen and cannot do anything even if the End button is over an empty space.
 
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