+1 on everything Rodney just said. The Quark is one of the best. How high off of the ground are you hovering? If you are only about 2 or 3 feet it could be cause of the rotor wash. Try hovering a little higher to get the heli into "clean air."
Oh, welcome to RCHelp. Like Rodney said, you will probably have better luck finding answers in the 600 section.