Your not the only one to have these problems with the Associated graphite chassis.
As bersercoe said, it can be any combination that will make it good or bad.
One little suggestion that will help a bit, use a LOSI idea and drill your arial tube about 10 mm above the chassis mount and run your arial wire through that point, dont run the arial lead through the chassis, mount the receiver on its side, crystal to the top, on 3 or 4 layers of double sided tape.
Make sure that your battery slot is insulated from the battery both sides and bottom.
just a few suggestions to help you out.