One of the guys at our club just traded for a Sukhoi 40 by Midwest. I flies great except when he makes a sharp bank say 70 or 80 degrees. It gets about half way through the bank and then banks sharply the other way sometimes going all the way inverted. It does it every time. He changed the pushrods thinking they might be bending. All control surfaces are tight. He's a great pilot. We can't seem to figure it out. Anyone out there having similar problems???