I'm debating between ZM lenses and Leica lenses in the future. I know it's high-contrast vs low-contrast, Made in Germany vs Made in Japan, flare-free vs flarey, etc.

One of my concerns is build quality. I fear that the ZM's might have some quality control issues. I've never held one in my hand, but do they feel substantial? And the wobble, is it a DIY fix?