So we just got two new 4000 batteries and a low voltage alarm. This morning we got set for a flight and while taking off slowly it tipped forward and rotors hit the ground. Took it inside and plugged it in and did a TX calibration and a basic IMU calibration. Next flight it lifted off and immediately went to the right rear about 20' very far and flipped. Took it in and did an advanced IMU calibration. Now it flies well again. Oh, and the prop guards are back on! Not sure why it was so off like that. It hasn't had and hard bumps yet before that.