The strange thing is that none of the old USSR made lenses were intended for the Leicas in any shape or form. And the J-3 and J-8 design was from CZ in the first place then modified to use with Zorki cameras. And Zoris were based on FEDs and FEDs were based on Leica II's. By "based on" I mean starting out like them but being modified along the way, sometimes for the better. (I'm thinking of take up spools, RF colouring and cable release arrangements and so on.)
A lot of people selling them on ebay etc say they are for Leica, FED and Zorki and when they don't work or the original design works the way it always did the makers get blamed.
Then there's the other factor, which is the age and condition of the camera bodies. I doubt if there's any normal (non-billionaire) user who has had the RF and the registration of all his FED, Zorki and Leica bodies adjusted and standardised and the same goes for the lenses.
Add in focus shift and you get a real dog's dinner...