It sounds to me with my limited retina experience (I have a iic I occasionally shoot and had a iiic which I stripped and rebuilt, but never could keep the shutter reliable) that it is gummed up and needs a CLA. Not sure about the rangefinder, but I am nearly positive the shutter will just be glued up with old lube.
Depending on how you feel, it is fairly easy to expose the shutter innards by going in from the front. You can try the lighterfluid cleaning routine, perhaps followed by sparing use of light oil.
My experience is my iic would stick, I'd clean it with lighterfluid and in a month or three it would stick again. In the end I used some watch oil and lubed it slightly more than "sparingly" - i.e. a small-medium drop on every bearing and contact point, on the basis that if it all went wrong and the oil got everywhere, it would still need a CLA and I would be no worse off. So far, no oil on the shutter blades and it has remained snappy for months now.
I like the retina - fun to shoot with as it looks and feels like it is from another era (which it is), but its small and has a good lens.