Oops, flying my P3S routinely about 30 feet up, a propeller came off, the craft fell to a relatively soft crash in thick tall grass, but did hit the ground upside down, with camera up. Nothing was visibly broken. Setting up again with carefully tightened props, compass calibration fails repeatedly. Switching launch location to an open field far from buildings and structures doesn't help. It is obviously possible that an internal component is broken or failed. Any other suggestions? Thx.