I took my ZI to my local repair guy who has worked on Leicas & CV's & he broke the shutter. After telling me over the phone how well made it was, he of course trashed the shutter as being poorly made after he broke it. It had to be sent back to the factory for repair. I had never had a problem with the shutter before that & have never had a problem since.
Rich Schleuning has told me that the rangefinder is complicated to adjust & that the adjustment should be done at the factory. After my experience, I'll take his word for it.