I was finally able to reproduce the problem so now I know what was the cause. This had been driving me crazy because it was so unpredictable and did not only happen when the aiming triangle was not on screen in the new view (player view after switching back from zoom view) as Scott described.
The problem occurs if you hold the mouse button down after moving your aim spot to a new point and then switch back to player view using the spacebar without releasing the mouse button. Now when you release the mouse button in the player view the aiming point jumps to the cursor location in that view.
I'm surprised that more people do not experience this problem but i suppose that most do not use the spacebar to toggle views or else they are not as slow as I am in releasing the mouse button.