I think you guys are right about not putting pressure on the lockbar. I think this raises the issues that will probably cause me to return the knife.
1. Right-hand bias in the design that impacts usability for LH users. Of course, all frame locks (unless specifically made for a LH user), have a built-in bias to RH users. This is usually only an issue for one-handed closing, usually not an issue for opening the knife if it has an ambidextrous thumb stud and flipper without too much resistance. For example, my ZT 0561 opens perfectly fine with my left hand, no problems despite the RH-centric design. I've even gotten good enough at closing it one handed that closing is not a problem, either. If the new ZT 0452cf opened and closed as easily and safely one-handed as my 0561 does, we wouldn't be having this discussion, I'd be a delighted user. But as a LH user, the design of this knife means it's always going to be harder doing one-handed opening. It's hard to both get a good purchase on the knife as a lefty, AND avoid gripping the frame lock to enable smooth opening.
2. Potential safety issues in the design. I've noticed two potential issues. One is, due to the slim handle design that's barely wider than the blade, when the knife is closed, the blade is exposed only about 1/8" inch below the surface of the handles on the side of the knife where the flipper protrudes from the back. This has potential to cut anything that slightly extends in between the handle area. Secondly, the relatively small flipper seems like a hazard for one-handed closing. Normally with other flippers like my ZT 0561, I can close with one hand by pressing the frame lock to one side, and letting the flipper come down and catch on my thumbnail to stop the blade closing on me, then just move my thumb out of the way and let it close. On this knife, while flipping and testing it carefully last night, 3 times at least the small flipper slipped off my thumbnail while closing one-handed, and the blade came down and could have easily cut into the top of my thumb if I hadn't been super careful. There's no such risk with this on the ZT 0561 and other flippers I've had; they have larger flippers and these always catch on your thumb with room to spare.
I'm still gonna keep this knife and test it for a couple more days, but these are the main issue I've noticed that concern me. It's clearly a quality knife, handle, and blade. But the basic design details concern me for the reasons above.