People use non-locking knives all the time and aren't reporting this issue so if knives that are supposed to lock are closing on people it still means that they are not using the knives appropriately or in a safe manor. A lock on a knife is a mechanical device and everyone knows a mechanical device is something that can and will fail. A lock on a knife is meant only to supplement your own safe knife handling and is not a magic talisman that prevents stupidity.
This kind of stuff was why, as a kid, I learned "you get what you pay for". Hard to believe it got by for 10 years without them noticing it wouldn't lock up.