Not going to argue the opinion that they can't fail but I will tell you fact as noted by my brother in law who has over a decade of professional wrenching under his belt.

He's seen them fail. Whether due to operator error or mechanical failure he didn't say but he did say that he'd never use them.

Against his better judgement and since I already have a pair, I'll go ahead and use them, but I'll sure be careful that they are seated properly.