Looks like you were hit by something because when i slow it down frame by frame the camera was knocked sideways out past the left front leg where you can see a picture of the front leg and arm with propeller on there spinning... i've had motor failures before and usually it will cause the aircraft to start wabbling and descend spinning from the tork of the other motors... then tumbling down, look like it got hit and started losing altitude because from the shadow on the snow it was coming down level all the while trying to recover then bouncing off the snow and starting returning to its last height until you hit RTL... interesting to see flight logs.