This has happened a few times but while in the badlands a short fall (like less than 5 ft) specifically falling off or on rocks can instantly kill. Its already happened a couple of times really annoying.
It's actually part of the story/world building. Your cyber legs aren't made for uneven ground, they are missing the pattelar tendon reflex – it's just too complex to reproduce cybernetically. And with all the power in the legs, when you stumble, you can't stop it and you just smash your whole face in. (That's also how Adam Smasher got his name. He knows how to use that weakness to his advantage: He just stumbles and uses that falling power to headbutt his enemies.)
Happened to me the other day in the Nomad prologue. I fell from the radio tower, but managed to survive. Then i tried to jump to free myself from the narrow place i had landed on, and ta-da!, i was dead all of a sudden.