I received a Phantom 2 Vision+ last Friday from the DJI Store online. I have had a couple of Phantom 2 Visions, so I am an experienced user. I upgraded the firmware, calibrated the remote control and calibrated the compass before trying to fly my new Phantom 2 Vision+. The motors didn't sound right when I first turned them on; one or more motors seemed to have a lower pitch than the others, and may have been running slower. I tried to fly anyway. My Phantom 2 Vision+ tipped over to the back the first time I tried to take off, damaging a prop. There was no wind, not even a breeze. This never happened to me in 23 flights with my last P2V - I'm always careful to get off the ground quickly to avoid tip-overs. I tried to fly a second time, and the same thing happened: another tip-over to the back. On my third try, I managed to get my Phantom 2 Vision+ in the air, but it still didn't sound right and seemed to drift a lot more (horizontally) than my previous Phantom 2 Visions. It seemed sluggish; it went up very slowly when I applied full throttle. I caught it in my hand (I try to always catch my Phantoms in my hand when landing to avoid tip-overs), turned the motors off, recalibrated the compass, and successfully took off again. On this final flight of the day, the motor sounds still seemed off, I still had more horizontal drift than my previous Phantoms, and it still seemed sluggish. This time, it started to drift downwards as well. I brought it back up several times, but it seemed to drift downwards at a higher rate each time. It finally drifted all the way to the ground and tipped over again, damaging a couple more props. It had about 50% battery power remaining at that point. It was not responsive to full throttle the last time it was coming down. I sent an e-mail to DJI Online Sales requesting a return; they still haven't responded, and it's been nearly a week. I called the US office, but they said they didn't have any in stock and it would take 4 weeks to repair. I contacted my CC company, but they've been ambivalent about whether they could do anything. I tried a few more flights today. I calibrated the IMU and recalibrated the compass a couple of times. I used another battery to make sure it wasn't a battery problem. It seemed to fly better; it took off fine, it wasn't sluggish, and while it drifted a bit initially, it eventually seemed to stabilize and flew quite well. Gimbal stability was impressive. Unfortunately, the downward drift started again around 15 minutes into flight. I noticed that the altitude indication was about 50 feet and didn't change as the P2V+ approached the ground. It drifted downwards, but was still controllable; I was able to catch it on landing after the low battery alarm went on. I did a final flight today with the original battery, fully charged, and it flew well, though the downward drift started again after 15 minutes or so. The downward drift gradually became so bad that once again it was unresponsive to full throttle and it landed a bit hard, tipping over and destroying a couple more props. The altitude indication was about 10 feet, even though it was on the ground at the home point. There were 12 satellites in view, so the GPS signal should have been good. I did the final flight at a location where I had flown P2Vs many times without incident. Any ideas on what could be causing this problem? I'm not sure whether an altitude sensor, a motor or software is to blame. It doesn't seem to be a battery problem, since I had the same problem with two different batteries.