Glad the unhook/rehook option helped you. there isn't a way in the codrone library to test different arm motors. without seeing the arms, it is hard to determine if there is a contact issue, wiring, or ESC ya, the landing is a tad tough sometimes. I'll do some runs of dropping the throttle in stages then land and see how that goes. though I've seen when flying and using throttling, the min distance is roughly 20cm (200mm) and the CoDrone likes that gap. forcing it lower will be interesting to see (I've tested going higher because the landscape I'm flying over had buildings [HO gauge table top] and the drone's flight goes up and down which alters the straight line path). calibrate(): I've found this only works the first time called (doesn't takeoff/land like the instruction says though) successive calls to calibrate() (I was gauging power levels @1 sec to get a feel of distance it travels and how straight of a line it goes) and I had a loop set int he program with successive calibrate()s but the first call changed the lights/paused, but each other successive calls did not.