Hi all, newbee here. My question is in two parts. I have Phantom FC40 about 12 months old. Just noticed after flying today one of the motors feels a bit notchy and has a little bit of play in the bearing, flies fine at present. I think I shall change the motor, are they all the same, and is it ok to change just one or should I change opposite pairs. Secondly if a motor fails in flight do they fall like a stone or do the others somehow compensate. Any help appreciated.