I have a new Phantom2 and on three different flights I have encountered a problem when doing a descent. Part way thorough it does a little wobble, becomes unresponsive and keeps heading down to the ground. Luckily I have been flying low and slow while learning and always over soft ground so no damage until today. The wobble happened during the descent of the FTH sequence and hit pretty hard from about 20 feet up and bent a strut. Any ideas?