Previously landed to change the battery nothing out of the ordinary, landing was smooth. Second time around I hovered close to my landing like before, and pressed the button (Motion Controller) to land. The drone quickly dropped made contact with the ground. full power applied and flipped over and crashed. WTF?

Maybe you activated turtle mode...

Hi there. Thank you for reaching out and we're deeply sorry for the incident that happened to your unit. Could you please confirm if you did experience an error message on your DJI Goggles during this incident? Is there any damaged to the unit? Try to have a test flight in an open area and see if the issue persists. Please keep us posted. Thank you.

this happens due to error in vision sensors .. recalibrate them via the assistance software

Possible GPS/Magnetic compass issue. Metal rods / Rebar under the concrete may have set it off... get yourself a landing pad and land on turf instead. This has happened to me once also... the issue I think was metal under the concrete. In part it almost seemed like the drone could not detect that it landed and kept trying to descend to land... it thinks it is still not on the ground. Also check the camera (sensors) on the bottom make sure they are clean. (unlikely the issue)

Recalibration of all the sensors also... I agree with above.

I kinda don't buy the downward sensor argument, at least in a way where I go "okay, that's acceptable drone behavior." I've had times where the drone says it can't land because of the visual sensors, and that is how it should work. Under no circumstances should a drone with sensors needing routine (?) calibration be flipping the drone over then throttling up to full power WHILE UPSIDE DOWN. This has happened to me and the drone would not shut down the motors until I turned the controlller off. Also, doesn't the Avata have an accelerometer to detect when it's upside down when it shouldn't be? Like, the accelerometer says "I'm upside down and I'm not supposed to be, shut down the motors," which is what happens if you grab it mid-flight and flip it. To me, this is a significant firmware issue and it makes me afraid to fly the Avata anywhere that isn't just absolutely remote and deserted.