I finally got my E-Flite Ultimate geared up yesterday and went for the maiden. I was holding it running the motor to see how much it would pull and after about half throttle the spur gear moved forward on the shaft and disengaged itself from the pinion gear. It did this a few times. When you slide the spur back it seems to engages the splines pretty tightly. I am using the stock E-Flite gearbox and Himax brushless motor. Any ideas?