Banggood WLToys V959 212 quad copter problem - not stable / balanced

http://www.banggood.com/Wholesale-WLtoys-V959-2_4G-4-Axis-4CH-RC-Quadcopter-With-Camera-Mode-2-p-59263.html Just received this the day before this video. It was working ok at first but now it's not balanced and wants to move backwards. Either the two rear/black ones are too weak or the ones in the front are too strong. ...or it's lost its ability to get a stable baseline from its gyros during initiation. Will work with Banggood to see what they can do. July 15 update: Banggood wrote me back immediately that they'll ship a new control board out immediately!