Misery loves company! I'm glad I'm not the only one this is happening to! Everything stated has happened to me too and to a friend. Sucks when I'm in an STF and the cube is about to explode when suddenly my throttle jumps down with me sitting right next to it!
If you depress left mouse button while on the throttle interface but release the mouse button while off of the interface ( eg screen center ) the mouse movement then controls the throttle when in the lower part of the screen (the region corresponding to the height of the throttle bar).
This continues until you left click - release while on the throttle interface.
ticket ID #1,287,605.
Thank you! You have solved the mystery. We will put in a fix for this.