I recently purchased a RTF Quad from Helipal that has NazaV2. The first flight was flawless. The second time when I landed and tried to shut the motors off with stick command the motors increased rpm. I took off again and then landed then tried to shut the motors off. Same thing. I did notice when I lifted off the quad did try to tip over unlike initial take off. I let the quad hover and grabbed it and told my buddy to stick command to shut the motors off. When he did this the quad really increased Roma and the motors shut off. What could cause this. Compass cal has been done and led indicator light is normal.