I also had problems with a z series ziess. I've also had problems with Savarski and Leupold. At least the Leupold was fixed fast.

So far my two schmit and benders work very well. I've never had a hicup and I've beaten them to near death. I have a 1.5-6x42 and a 3-12x50, Both have been on weatherby mags, 300, 340 and 416. They work great.