Well, It's definitly an electrical problem! Could Be a bad Servo, The Servo that's Moving by itself with no input, Is that the Servo hooked to the tail rotor? Or is it another servo? These Coronas use BEC system so it may be happening at the end of the flight because thats when the power pack may not have enough power to hold everything under control, and the bad servo starts acting up. Did you say you changed the Receiver already? Get back to me, let me know I want to try to help U solve this problem....