After many successful flights, the other day I installed the latest firmware upgrade and Go App. It installed successfully, and before I took it to a park across the road to confirm it was all operational, I successfully recalibrated the compass, the camera gimbal, and the IMU. The GPS locked on 16 satellites. At the park I used the automatic takeoff button on the RC, letting it hover for a minute as recommended. Surprise, surprise, surprise... when I pushed forward on the left stick (altitude control - up), nothing happened. Nothing happened when I pulled back on the control to land. Pushing left and right on the left stick had no effect. Similarly the right stick control was not working. However, the automatic land button worked fine. I tried this several times but although the RC takeoff / land buttons worked, the joy sticks had no effect at all. In desperation, I re-linked the RC and went out to try again. Miraculously, it was all working again. I'm baffled. If the RC link to the Phantom was dead, how could the takeoff and landing button worked? Clearly, there is something I don't understand about the unit.