After a hard landing, I am having issues with out of control flight. Bird goes up and down with no movement of sticks. Would crash if I didn't over ride what it is trying to do. I didn't think I was going to get it down. I was calling it down and it would descend a bit, go back up, start coming down until I could finally grab it. Setting on the table I can watch the altitude fluctuate. It starts out not so bad. 5 to 6 feet, but after a minute or two it will range from 27' to +60', down to -150', back up to 50', down to -200' and so on. I have done a advanced IMU calibration several time "with unit cool", & calibrated compass. After my last flight, I not sure if my hard landing caused this issue, or this issue caused my hard landing? Any suggestion? I am stumped!!!!