Most spine-locks, I've found, do not have a tightly squared "lock-block" that drops into a tightly squared lock-notch in the blade. There is a slight amount of slop, that allows the lock to function with basic care(grunge space). What that means is that between the pivot pin specs, lock-notch, and lock-block, it may add up to almost .010 of "slop"- which gives you that play, with strong downward pressure. The same thing will happen with a liner-lock, you just won't notice, until you go to close it, and the liner is really wedged in place!, I've notice that when I press down on the Native to cut through nylon ropes and cords, I can feel the blade moving, like the lock doesn't hold securely. Ahhh - I should have posted that in the knife forum - maybe I'll do that.