Yes, there is a problem. The focusing helicals on the Nikon cameras and Contax cameras are somewhat different. Consequently, on lenses larger than 35mm, the rangefinder will indicate that the image is in focus, while the image is not actually in focus at the film plane. This problem will not be apparent with shorter lenses like the 35mm because the focusing error will be within the lens' depth of field. The focusing error gets progressively greater as the focal length is increased.
Brian Sweeney and others could probably give you the technical explanation.
dexdog