Brown trouser moment for sure - high AOA, ice and then your CoG changes without warning..............................
"As reported by Aero Magazine, the KC-390 registered PT-ZNF was performing critical pre-stall tests, that involved high-AOA (Angle Of Attack) and ice formation on wings. During the maneuver, an equipment used for the tests, detached from its place and rolled to the back of the cargo compartment causing a sudden change in the center of gravity (CG) of the aircraft. As a consequence of the rapid displacement of the CG the pilots lost control of the airlifter, that stalled and started to spin towards the ground. Reportedly, the pilots were able to recover the aircraft as it was only 1,000 feet (about 300 m) above the ground, and landed the KC-390 safely in Gavião Peixoto airfield."