After powering up the A/C w/o props ,I tilt it forward and back then set it down..The motors are still thinking it’s off level . I can move the throttle and is slow to respond .I did a IMU calibrate still the same issue. I tried with props on and it just to unstable it just flipped and motor made a horrible screech. Any clue to the issue I’m having. I’ve never flew this phantom before.