Yes I have had a couple of welds fail on a set of Grand Auto specials, stamped steel type, jack-stands... That were properly placed etc. & almost crush me under the 68 Charger I was working on... I was trying on some new 15x10" Cragers & N50-15's & some 15x5"s up front {back in the late 70's}, jacked car up in the garage, on a flat surface etc., put the jack-stands under the rear axle tubes & under the sub-frame on both sides in the front... Rocked the car in all directions just to make sure... Proceeded & I took off all the old wheels, trial fit the new ones, made sure they fit 1st... Then got under the car & started to do a shift-kit, deep trans-pan & ratchet shifter... I only had one rear tire actually installed... fast forward I heard a pop noise, I climbed out... I was wondering/contemplating if it was the punk kid across the street, he had shot a couple of my cars with his BB gun in the past {long story}... I saw nothing so got back under the car again & continued to do the trans work, I had just finished up the trans & was re-bolting in my cross-member... Now I heard a big loud pop this time... I got out again, went across the street banged on the punk kids door & torched the father, gave him a piece of mind about his POS punk kid shooting my car again {so I thought}... I went back across the street got under the car again, the car just fell, while I was under the car putting the drive shaft back in... Thank God, I had the one tire on or I'd be dead/flat crushed for sure, it split the old wood creeper I was on, literally in half... I was able to barely get out from under the back, on the side that the tire was on, the car was now partially sitting on the "now broken POS jack-stand"... No-one was home, to help me either... I had a kind of sore arm & sore chest, but needed my car finished, to go to the hospital, so I put the rest of my wheels & tires back on, finished bolting in the drive shaft, car now sitting on wood blocks... I got to the hospital... Now sitting in the waiting room to get service finally, just scratching my chest, now holding my aching arm, my fingers literally went into my chest, between the 2 sides of my ribcage... I had broken/split my sternum in 2... I freaked out & started yelling, they took me in & medicated me up, they said I was probably in shock & my adrenaline was only thing keeping me going, is why I was able to even get to the hospital... I was lucky, I didn't puncture my heart or lungs... Anyway they fixed/splinted my fractured arm & wrapped my chest for the broken sternum {not much they can do, except keep me immobile}... It was at-least 6+ months before I could race or work even again... I never did apologize to the punk kid or his father, that punk kid got a real beating too... I should have sued Grand Auto, but people just didn't do that stuff, very much back then... sorry for the long story... but yes I had a jack-stand fail...