I have been able to get mine to slip just by testing them with the smallest of either taps on a softly padded table or by putting static pressure on the spine of a couple of them. The taps to the spine are a moot point. I dont put much stock in spine whacking, but it puzzles me that less expensive knives of mine won't slip when tested the same way.
The ones that slip due to constant pressure to the spine worry me more. Especially since one is an Emerson model with a wave feature pretty much designed to potentially be a self defense weapon.
I have only had one ZT slip its lock in the wild and that was a 350. Fluke event as I was reaching under a hot tub and trying to snap cut a wire at an odd angle. No pressure on the lock with my hand it just sort of bounced off it the lock face, but the AO spring pushed it back into lock. No harm done.
I would use your Kershaw/ZTs without hesitation. When you hold them correctly I don't think you'll have an issue. I still don't like that I can get mine to slip so easily for what I spent on them though.