Hey guys. So I have a ZT0551 and I love it. Today I bought a ZT0350. Got it from Bass pro. Serial number is 49xxx. I've seen these spine wack tests. Some of the ZT knives in the videos fail. This is confusing. Was it the early ones or what? I have taken both of mine and spine whacked both of them over and over. They are rock solid. No failures. Somebody school me on all this. I freaking love this 0350 and i want to have strong confidence in this knife and daily carry it.