It looks like you were using the nifty-lifty and the floor-jack failed, and the nifty-lift to slipped off and the jack punch through the diffuser? I also use the nifty-lifty to lift up the rear, then slide ramps under the rear wheels before removing the under tray, which has the same risk before the ramps are in place. The nifty-lifty slipping off has always seemed like a risk.
That's a good idea, but has always seemed too low to do easily, particularly putting the undertray back on with the car back on the ground. Is putting it back on difficult with it on the ground? I've thought of getting a cordless ratchet, which would be helpful with the car on the ground.
Good reminder though that I should be using front wheel chocks while lifting the back. And to be a little paranoid about lifting safety.
I just dont see the jack failure here. Sorry. But if the jack hydraulicly fails, it is going to go DOWN. In the pic it looks like car rolled and jack (still extended) punched a hole in the diffuser.
Not meaning to hurt anyone's feeling, but I am doubting the mode of failure as presented.