h-quad quadcopter

I have recently built a H-Quad (flitetest's) and I put some of the cheap 24gram motors from hobbyking on the frame however I have now realized that A they are vastly under powered and B that they are SHOCKING quality, there were little chips of aluminium in the magnets and some around the...

I'm still tuning my H-quad but managed to get some good footage with a Creative Vado 720p camera mounted to the front. Any idea what causes the oscillation problem that happens at about 1:30?